Survival on the ark: life-history trends in captive parrots



This article is corrected by:

  1. Errata: Erratum Volume 16, Issue 5, 595, Article first published online: 22 October 2013

  • Editor: Iain Gordon

  • Associate Editor: Iain Gordon

?Anna M. Young, Department of Biology, MSC 3AF, New Mexico State University, Las Cruces, NM 88003, USA?Tel: +1 575 646 4863; Fax: +1 575 646 5665?Email:


Members of the order Psittaciformes (parrots and cockatoos) are among the most long-lived and endangered avian species. Comprehensive data on lifespan and breeding are critical to setting conservation priorities, parameterizing population viability models, and managing captive and wild populations. To meet these needs, we analyzed 83 212 life-history records of captive birds from the International Species Information System (ISIS) and calculated lifespan and breeding parameters for 260 species of parrots (71% of extant species). Species varied widely in lifespan, with larger species generally living longer than smaller ones. The highest maximum lifespan recorded was 92 years in Cacatua moluccensis, but only 11 other species had a maximum lifespan over 50 years. Our data indicate that while some captive individuals are capable of reaching extraordinary ages, median lifespans are generally shorter than widely assumed, albeit with some increase seen in birds presently held in zoos. Species that lived longer and bred later in life tended to be more threatened according to IUCN classifications. We documented several individuals of multiple species that were able to breed for more than two decades, but the majority of clades examined had much shorter active reproduction periods. Post-breeding periods were surprisingly long and in many cases surpassed the duration of active breeding. Our results demonstrate the value of the ISIS database to estimate life-history data for an at-risk taxon that is difficult to study in the wild, and provide life-history data that is crucial for predictive modeling of future species endangerment and proactively management of captive populations of parrots.


Earth is facing a biodiversity crisis of enormous proportions, with extinction rates estimated to be 1000–10 000 times greater than normal background rates (Wilson, 1991; Brooks et al., 2006). Zoos and aquariums play a critical role in conserving biodiversity (Miller et al., 2004) through research, education, conservation of habitat and genomic materials, and captive breeding (Fischer & Lindenmayer, 2000; Price & Soorae, 2003; Foose & Wiese, 2006; Mace et al., 2007; Walters et al., 2010). Captive breeding maintains viable populations and in some notable cases provides the only source of individuals for reintroductions (Beck et al., 1994; Seddon, Armstrong & Maloney, 2007), as with the black-footed ferret Mustela nigripes (Biggins et al., 1999), California condor Gymnogyps californianus (Snyder & Snyder, 1989), Przewalski's horse Equus caballus przewalskii (Bouman, 2000) and Arabian oryx Oryx leucoryx (Rahbek, 1993). Another important, albeit less widely recognized, role for captive populations is to provide behavioral, physiological and life-history data that are difficult, costly or time consuming to obtain in field studies (see Ricklefs & Cadena, 2007). These data are useful for predictive modeling and management of wild populations and for setting management priorities for captive populations (Conde et al., 2011).

One important step in managing captive populations is to assess conservation priorities at the larger taxonomic scales of family or order. Zoos and aquariums have organized Taxon Advisory Groups (TAGs) to set priorities for maintaining and managing captive populations across higher-level taxa. TAGs determine which species to propagate based primarily on captive population numbers and conservation status (Wilkinson, 2000; Hutchins, 2003; Association of Zoos and Aquariums (AZA), 2007). The TAGs further divide species into Regional Collection Plans (RCBs) which are represented worldwide. All of these programs were initiated in the 1980s to track and manage the genetics and demographics of captive animal populations in studbooks so as to meet overall management goals for that species (Hutchins & Wiese, 1991). A critical role for TAGs is to prioritize efforts across different species because both space and funding for captive animals are limited (Hutchins & Wiese, 1991; Smith et al., 2002; Hutchins, 2003; Baker, 2007).

TAGs face the issue of surplus animals, animals that have already made a genetic contribution to the program either directly or via kin (Hutchins & Wiese, 1991; Lindburg & Lindburg, 1995), and are now consuming resources that could otherwise be invested in breeding animals that would further enhance genetic diversity. To allocate limited zoo resources optimally, TAGs should work with RCPs to predict and control numbers of surplus animals (Lacy, 1995; Lindburg & Lindburg, 1995; Graham, 1996), a task which requires comprehensive data on a species' lifespan, breeding parameters, IUCN status, current numbers and demographics. Demographic and reproductive data are especially important for captive breeding programs (Hutchins & Wiese, 1991; Hutchins, 2003), and authors of captive-management manuals have been advised to incorporate data on lifespan and duration of active reproduction to improve breeding and reintroduction efforts (Jackson, 2003; Seddon et al., 2007). These recommendations have been followed in a few cases, most notably for elephants (Wiese & Willis, 2004; Wiese & Willis, 2006; Hutchins & Thompson, 2008). However, the comprehensive life-history data needed for optimal management of captive populations are not readily available for most taxa (Baker, 2007; Hutchins & Thompson, 2008).

Here we provide comprehensive lifespan and reproductive data for the order Psittaciformes (parrots and cockatoos, hereafter ‘parrots’). The parrots are an important group in which to investigate general patterns of captive longevity and breeding. The order contains a high proportion of endangered species, with 36% of the 365 extant species of parrots (Forshaw & Knight, 2006) listed as being at risk (IUCN, 2009) and at least 18 confirmed extinctions by the end of the 20th century, making parrots the most threatened speciose order of birds (Forshaw & Knight, 2006). They are also the longest-lived order of birds for their size (Prinzinger, 1993) with some reported lifespans exceeding 50 years (Brouwer et al., 2000). Furthermore, they are commonly held in captivity, with upwards of 20 000 parrots housed in zoos and other animal holding facilities [International Species Information System (ISIS), 2009] and millions more held in private hands (World Parrot Trust, 2009). Successful reintroductions with captive bred parrots are challenging (Snyder et al., 1996), but feasible (Sanz & Grajal, 1998; Collazo et al., 2003; Brightsmith et al., 2005; White Jr, Collazo & Vilella, 2005). The majority of bird supplementation in the wild has come from captive breeding programs (Fischer & Lindenmayer, 2000), but these efforts are stymied by a lack of captive breeding populations for many species of high conservation concern. Instead, the current zoo population of parrots is biased toward large species that are more attractive to humans (Frynta et al., 2010). While the conventional role of zoos in the past has been entertainment (Hatchwell et al., 2007), the World Association of Zoos and Aquariums recently asserted that the “major goal of zoos and aquariums will be to integrate all aspects of their work with conservation activities” (WAZA, 2005). Overall, the large numbers, long lifespans and high level of endangerment of parrots results in a high burden on space in zoos and a critical need to set breeding and husbandry goals on the basis of conservation priorities.

Efforts to set conservation priorities for parrots have been hampered by a lack of life-history data. While there are a few exemplary studies of life-history and reproduction in wild populations (Saunders, 1982; Buckland, Rowley & Williams, 1983; Rowley, 1983; Powlesland et al., 1992; Sandercock et al., 2000; Heinsohn & Legge, 2003; Murphy, Legge & Heinsohn, 2003; Renton & Salinas-Melgoza, 2004; Beissinger et al., 2008; Koenig, 2008; Holdsworth, Dettmann & Baker, in press), it is difficult to age adults and field studies are generally short in duration relative to lifespans. While data from captive individuals may not precisely predict lifespans in wild animals given the different stresses faced by each, a significant positive relationship between captive and wild maximum lifespans has been demonstrated generally in birds (Wasser & Sherman, 2010) as have similar rates of actuarial senescence (Ricklefs, 2000). Previous studies in parrots have provided some data on captive lifespans: Brouwer et al. (2000) reported maximum recorded ages for 176 species and subspecies of parrots, while Vanstreels et al. (2010) examined lifespans of confiscated wild-caught parrots in a Brazilian zoo. Neither study reported reproductive parameters. Parrot studbooks are maintained regionally and internationally, but less than 10% of all parrot species and subspecies housed in zoos are currently represented by studbooks worldwide (L. Bingaman Lackey, pers. obs.). In sum, these sources provide valuable information for some species, but there remains a pressing need for comprehensive life-history data for the order as a whole.

The ISIS database contains thousands of records of parrot births, deaths and reproduction contributed by zoos and other animal holding collections from c. 845 member institutions in 80 countries (ISIS, 2009). This database represents a wealth of valuable information on parrots, and many other taxa, which has been largely untapped by the zoological and scientific community.

We provide a species-level analysis of ISIS records to present comprehensive life-history data for parrots. We collated data from over 87 000 individuals representing over 260 species of parrots from the ISIS database to characterize lifespan and breeding parameters for each species, examine general patterns across major clades of parrots, and test the effects of mass and sex on lifespan.


Data coding

We compiled individual lifespan records representing all available parrot species from ISIS. We used Forshaw & Knight (2006) as the taxonomic authority for common and scientific names. Our only departure from the classification of Forshaw & Knight (2006) was to elevate the three subspecies of rosellas under Platycercus elegans to full species based on Joseph et al., (2008): the crimson rosella P. elegans, the yellow rosella Platycercus flaveolus and the orange-red and yellow rosella Platycercus adelaidae; otherwise we did not distinguish between subspecies. Individual birds that hatched in an ISIS facility received a HATCH date, while those that were transferred into an ISIS facility from a non-ISIS institution received an IN date. Birds transferred out of an ISIS facility received an OUT date, whereas birds that died in an ISIS facility received a DEATH date. We eliminated individuals with records that had an IN or HATCH date before the 1800s, or which were missing these dates entirely. We excluded individuals recorded as surviving less than one day from further analysis. Sorting and formatting of the data were conducted with Access 2003 (Microsoft Inc., Redmond, WA, USA), and statistical analyses were run using JMP 8.0 (SAS Institute, Cary, NC, USA).

Lifespan across species

To reveal trends in basic lifespan data across species, we first calculated the median lifespan and maximum lifespan for each species. Preliminary analysis indicated that many species followed a Type III survivorship curve (Ricklefs, 2008), with high initial mortality that reached an asymptote at 4 years of age. Thus we calculated lifespan statistics on two different datasets: (1) all individuals who lived past their first day; (2) individuals who survived to age 4 years or older. Four years exceeds the age of first reproduction for many species included in the analysis, but preliminary analyses found this age to be the best single threshold for avoiding juvenile mortality across all 260 species analyzed. We also calculated the median living adult age for individuals that were still alive as of 24 March 2008 as a measure of lifespan for the currently living captive population.

We calculated the median instead of the mean as an indicator of central tendencies because the lifespan data were non-normally distributed and exhibited a positively skewed unimodal distribution (Zar, 1999). While we report these summary statistics for all species, for the purpose of statistical tests of life-history relationships we excluded species with fewer than 20 individual records to increase reliability of the data and ensure that general trends would not be distorted by a few aberrant individuals. We tested the effect of sex on the maximum and median lifespan by performing the non-parametric Wilcoxon signed-rank test, which treated the two sexes of each species as a paired comparison (Zar, 1999). We then examined the relationship between body size and lifespan with least-squares regressions of log of mass versus log of maximum lifespan, median adult lifespan and median adult age. Least-squares regressions of maximum lifespan versus median adult lifespan and median adult age were performed on log transformed data. Positive residuals from these regressions indicated species with a single individual, represented by the maximum lifespan, that lived substantially longer than their conspecifics, represented by median adult lifespan or age; negative residuals indicated species with a median adult lifespan or age that was closer to the maximum lifespan within that species.

Lifespan trends for clades

In addition to the summary statistics described across species, we examined data for species within selected clades of particular interest to zoos and captive population managers. These clades were (1) Cacatua and allies (Cacatua, Callocephalon, Eolophus); (2) Trichoglossus and allies (Chalcopsitta, Eos, Trichoglossus); (3) Platycercus and allies (Barnardius, Platycercus, Psephotus, Purpureicephalus); (4) Ara and allies (Ara, Orthopsittaca, Propyrrhura); (5) Aratinga; (6) Amazona. We again excluded species that had fewer than 20 individual records from these analyses. A generalized linear model (GLM) was performed to test for the joint effects of mass and clade on the means of maximum lifespan, median adult lifespan and median adult age and Tukey–Kramer HSD was used for post hoc comparison between pairs of clades.

Breeding parameters

To describe breeding parameters for each species, we analyzed ISIS breeding information for female parrots. Males were not included in this analysis because paternity could not be unambiguously determined. For these analyses we excluded species with fewer than five individuals to maintain an adequate sample size while minimizing the effect of aberrant individuals. Several other types of exclusions were performed on the breeding data to balance maximizing the number of records available for analysis with maintaining accurate and conservative estimates of reproductive parameters (summarized in Table 1). We calculated medians of the age of first breeding, age of last breeding, duration of active breeding and duration of post-breeding. Values for age of last breeding are conservative estimates as birds with an IN date were treated as newly hatched birds. Values of the post-breeding period are also conservative because we treated individuals transferred out of the system as deaths. A one-way ANOVA was performed to test for differences in the means of these four breeding parameters among the six major clades.

Table 1. Criteria for calculation of breeding parameters
 Parameters usedTypes of individual records included in analysis
  1. ISIS, International Species Information System.

Age of first breedingKnown HATCH date, age at first breeding >0Birds that reproduced within an ISIS facility
Age at last breedingBoth HATCH and IN date used if age at last breeding >0Birds whose last reproduction was after their transfer into an ISIS facility
Duration of active reproductionBoth HATCH and IN date used if age of first reproduction >0Birds that reproduced within an ISIS facility, included durations=0, where an individual reproduced only once
Duration of post-active reproductionBoth HATCH and IN date used if age at last breeding >0, both DEATH and OUT date usedBirds whose last reproduction was after their transfer into an ISIS facility, included durations=0, where an individual died on the day of last reproduction

Conservation status

To determine whether conservation status is associated with particular demographic parameters, one-way ANOVAs were conducted to test for an effect of IUCN status on lifespan (maximum and median adult) and median breeding variables (age of first and last breeding, duration of active breeding and post-breeding).


Lifespan across species

We compiled 87 777 individual parrot records representing 262 species (72% of all parrot species) from ISIS. After excluding those individuals hatched before the 1800s or that failed to survive their first day, and species in which no individuals lived past a year, 83 212 individuals representing 260 species remained for analysis. Parrot species in captivity ranged dramatically in their maximum and median lifespans. The highest maximum lifespan recorded was 92 years for the salmon-crested cockatoo Cacatua moluccensis. Only 12 species (<5% of the 260 species) had an individual live past 50 years of age. Of all the species held in ISIS institutions, 50% never had an individual live beyond 22 years of age, and only 30% of these species had a median adult lifespan =10 years, even after limiting data to individuals who survived juvenile mortality (=4 years). In contrast, when only living animals were considered, 58% of species had a median age =10 years (Table 2, see supporting information Table S1 for medians with quartiles).

Table 2. Lifespan summary across species (in years)
Species common nameScientific nameLifespan: maximumLifespan: allaLifespan: adults =4Age: adults =4bIUCN statusc
  • a

    Does not include chicks that died day of hatch.

  • b

    Individuals that were still alive as of 24 March 2008.

  • c

    2009 Red List status.

  • LC, Least Concern; NT, Near Threatened; VU, Vulnerable; EN, Endangered; CE, Critically Endangered; EX, Extinct; NA, not available.

Palm cockatooProbosciger aterrimus39.975225.2929911.6014413.30LC
Yellow-tailed black cockatooCalyptorhynchus funereus47.413242.841369.786310.95LC
Red-tailed black cockatooCalyptorhynchus banksii55.263544.2018011.848213.02LC
Glossy black cockatooCalyptorhynchus lathami37.72415.32228.15139.07LC
Gang gang cockatooCallocephalon fimbriatum27.572912.07969.732513.77LC
GalahEolophus roseicapilla72.8218892.006879.3324910.08LC
Sulfur-crested cockatooCacatua galerita72.9516683.7180410.9230912.38LC
Yellow-crested cockatooCacatua sulphurea39.979774.154978.9022111.23CR
Blue-eyed cockatooCacatua ophthalmica37.95847.785011.662111.60VU
White-crested cockatooCacatua alba32.249673.494609.7622811.15VU
Salmon-crested cockatooCacatua moluccensis92.5516754.568969.5131411.07VU
Major Mitchell's cockatooCacatua leadbeateri74.869492.954199.6413512.00LC
Slender-billed corellaCacatua tenuirostris43.453331.9312611.705212.09LC
Little corellaCacatua sanguinea44.014552.4518911.525612.49LC
Ducorps's corellaCacatua ducorpsii57.81733.75369.58239.58LC
Goffin's corellaCacatua goffini30.395813.9028910.6513113.46NT
Red-vented corellaCacatua haematuropygia33.591255.306711.762812.02CR
CockatielNymphicus hollandicus35.9228502.539497.062418.98LC
Black loryChalcopsitta atra17.581402.78567.66159.64LC
Yellow-streaked loryChalcopsitta scintillata25.011762.13609.48209.03LC
Brown loryChalcopsitta duivenbodei26.542481.66698.903010.07LC
Cardinal loryChalcopsitta cardinalis18.23644.72379.702310.23LC
Dusky loryPseudeos fuscata19.595682.762397.341007.46LC
Black-winged loryEos cyanogenia22.531421.67437.0655.98VU
Violet-necked loryEos squamata18.231662.28586.57206.82LC
Blue-streaked loryEos reticulata27.833532.161217.913311.41NT
Red and blue loryEos histrio16.08566.14359.581810.48EN
Red loryEos bornea29.488812.783806.921457.86LC
Blue-eared loryEos semilarvata12.23144.06710.02610.82LC
Ornate lorikeetTrichoglossus ornatus18.491433.27626.45307.91LC
Rainbow lorikeetTrichoglossus haematodus37.9468052.3924246.4713256.70LC
Scaly-breasted lorikeetTrichoglossus chlorolepidotus24.171872.60726.62256.62LC
Olive-headed lorikeetTrichoglossus euteles18.741672.59637.40238.15LC
Yellow and green lorikeetTrichoglossus flavoviridis12.28332.27115.36  LC
Mindanao lorikeetTrichoglossus johnstoniae17.77811.85287.27128.79NT
Varied lorikeetPsitteuteles versicolor12.471731.42486.6428.47LC
Iris lorikeetPsitteuteles iris27.041471.58397.712210.01NT
Goldie's lorikeetPsitteuteles goldiei24.136051.611617.01318.90LC
Musk lorikeetGlossopsitta concinna19.304672.221415.88225.69LC
Little lorikeetGlossopsitta pusilla20.111531.41345.2769.75LC
Purple-crowned lorikeetGlossopsitta porphyrocephala12.674761.28815.4765.35LC
Blue-crowned lorikeetVini australis37.362412.05746.62319.51LC
Kuhl's lorikeetVini kuhlii2.2112.21    EN
Blue lorikeetVini peruviana21.12911.213011.66117.95VU
Collared lorikeetPhigys solitarius18.231063.66509.22369.99LC
Purple-bellied loryLorius hypoinochrous18.131210.661111.09611.19LC
Black-capped loryLorius lory30.834823.132197.561077.50LC
Purple-naped loryLorius domicella19.231812.79777.16299.00VU
Yellow-bibbed loryLorius chlorocercus13.811345.27878.884713.81LC
Chattering loryLorius garrulus27.245862.432207.59657.89EN
Red-fronted lorikeetCharmosyna rubronotata2.3432.30    LC
Red-flanked lorikeeetCharmosyna placentis19.591981.47565.91286.91LC
Fairy lorikeetCharmosyna pulchella20.78711.43216.65315.58LC
Duchess lorikeetCharmosyna margarethae4.0044.0044.00  NT
Josephine's lorikeetCharmosyna josefinae10.20223.57105.26  LC
Papuan lorikeetCharmosyna papou22.435521.381406.80338.23LC
Whiskered lorikeetOreopsittacus arfaki1.5621.56    LC
Musschenbroek's lorikeetNeopsittacus musschenbroekii26.54732.34267.23416.89LC
KeaNestor notabilis50.537732.8833910.4911410.80VU
KakaNestor meridionalis35.461912.136412.551712.25EN
Pesquet's parrotPsittrichas fulgidus27.631594.84878.29399.73VU
Orange-breasted fig parrotCyclopsitta gulielmitertii12.23112.23112.23112.23LC
Double-eyed fig parrotCyclopsitta diophthalma14.352871.81836.54166.47LC
Desmarest's fig parrotPsittaculirostris desmarestii17.461361.06255.29213.24LC
Edwards's fig parrotPsittaculirostris edwardsii20.401221.66367.3489.81LC
Salvadori's fig parrotPsittaculirostris salvadorii14.89143.6979.7339.73VU
GuaiaberoBolbopsittacus lunulatus1.9931.86    LC
Blue-rumped parrotPsittinus cyanurus15.23282.6096.85211.04NT
Red-cheeked parrotGeoffroyus geoffroyi5.5423.0715.54  LC
Blue-crowned racquet-tailed parrotPrioniturus discurus1.6440.06    LC
Golden-mantled racquet-tailed parrotPrioniturus platurus24.65174.79915.78424.65LC
Eclectus parrotEclectus roratus40.7625211.929499.0041610.08LC
Great-billed parrotTanygnathus megalorhynchos14.56241.9786.86114.56LC
Blue-naped parrotTanygnathus lucionensis13.19362.52105.90113.19NT
Blue-backed parrotTanygnathus sumatranus26.30106.8167.1837.18LC
Alexandrine parakeetPsittacula eupatria29.065625.063086.231815.23LC
Rose-ringed parakeetPsittacula krameri33.6317193.587977.692749.58LC
Mauritius parakeetPsittacula echo12.3566.7247.63210.43EN
Malabar parakeetPsittacula columboides14.08155.1887.24  LC
Emerald-collared parakeetPsittacula calthorpae10.59210.41210.41  LC
Plum-headed parakeetPsittacula cyanocephala19.864104.222095.621175.23LC
Blossom-headed parakeetPsittacula roseata17.15216.07139.07610.12LC
Slaty-headed parakeetPsittacula himalayana18.46196.82137.77117.77LC
Derbyan parakeetPsittacula derbiana28.224082.241679.07629.81LC
Nicobar parakeetPsittacula caniceps6.54140.4645.79  NT
Red-breasted parakeetPsittacula alexandri20.242823.031198.134710.23LC
Long-tailed parakeetPsittacula longicauda13.05551.68128.83710.23NT
Gray-headed lovebirdAgapornis canus16.011202.79457.12207.12LC
Red-faced lovebirdAgapornis pullarius19.231234.22627.55137.73LC
Black-winged lovebirdAgapornis taranta15.821642.38597.0126.16LC
Peach-faced lovebirdAgapornis roseicollis34.1019432.336636.741208.23LC
Masked lovebirdAgapornis personatus24.249971.462825.731065.56LC
Fischer's lovebirdAgapornis fischeri32.2414021.753975.942037.80NT
Nyasa lovebirdAgapornis lilianae19.202273.631087.4446.38NT
Black-cheeked lovebirdAgapornis nigrigenis13.756751.712246.831526.88VU
Vernal hanging parrotLoriculus vernalis13.00506.93398.10119.62LC
Ceylon hanging parrotLoriculus beryllinus3.5622.71    LC
Philippine hanging parrotLoriculus philippensis13.33214.14125.05110.23LC
Blue-crowned hanging parrotLoriculus galgulus21.258372.182536.33659.00LC
Maroon-rumped hanging parrotLoriculus stigmatus13.03244.37127.93  LC
Green hanging parrotLoriculus exilis3.4533.10    NT
Yellow-throated hanging parrotLoriculus pusillus2.2312.23    NT
Moluccan king parrotAlisterus amboinensis29.201121.94417.56178.16LC
Papuan king parrotAlisterus chloropterus22.35776.064510.261011.66LC
Australian king parrotAlisterus scapularis31.326991.531717.63597.75LC
Olive-shouldered parrotAprosmictus jonquillaceus14.84711.12611.18  NT
Red-winged parrotAprosmictus erythropterus27.303901.831379.034110.69LC
Superb parrotPolytelis swainsonii24.214212.861667.18476.81VU
Regent parrotPolytelis anthopeplus27.493652.511257.23367.21LC
Princess parrotPolytelis alexandrae23.986142.552107.36767.45NT
Red-capped parrotPurpureicephalus spurius17.901381.06298.00412.91LC
Mallee ringneck parrotBarnardius barnardi31.621811.05526.7584.84NA
Port Lincoln parrotBarnardius zonarius17.961403.66687.81138.06LC
Green rosellaPlatycercus caledonicus7.98373.37156.3546.61LC
Crimson rosellaPlatycercus elegans20.1410101.031396.50367.53LC
Yellow rosellaPlatycercus flaveolus13.31592.50216.1814.23LC
Adelaide rosellaPlatycercus adelaidae17.35580.26118.4457.23LC
Eastern rosellaPlatycercus eximius37.4413021.613346.58936.81LC
Pale-headed rosellaPlatycercus adscitus25.032671.76756.35237.18LC
Northern rosellaPlatycercus venustus21.571912.57696.8147.81LC
Western rosellaPlatycercus icterotis31.642741.03646.5875.87LC
BluebonnetNorthiella haematogaster15.401731.44406.06210.42LC
Red-rumped parrotPsephotus haematonotus17.747921.932385.271075.23LC
Mulga parrotPsephotus varius11.791161.93255.6134.81LC
Golden-shouldered parrotPsephotus chrysopterygius20.968121.382217.91329.49EN
Swift parrotLathamus discolor14.181841.26286.28116.24EN
Antipodes green parakeetCyanoramphus unicolor12.661472.77606.6175.37VU
Red-fronted parakeetCyanoramphus novaezelandiae36.455101.731297.235110.05VU
Yellow-fronted parakeetCyanoramphus auriceps16.481711.30516.54206.96NT
Orange-fronted parakeetCyanoramphus malherbi12.28171.8747.56112.28CR
Horned parakeetEunymphicus cornutus12.90302.75116.93611.98EN
Masked shining parrotProsopeia personata17.73411.46411.46  NT
Red shining parrotProsopeia tabuensis23.67355.42219.89  LC
Blue-winged parrotNeophema chrysostoma15.851650.60305.47  LC
Elegant parrotNeophema elegans14.912071.72546.22  LC
Rock parrotNeophema petrophila16.92682.17256.36  LC
Orange-bellied parrotNeophema chrysogaster13.274260.81816.29477.23CR
Turquoise parrotNeophema pulchella26.544612.151426.65157.52LC
Scarlet-chested parrotNeophema splendida25.4112841.052025.913213.05LC
Bourke's parrotNeopsephotus bourkii19.405112.111556.06436.56LC
BudgerigarMelopsittacus undulatus18.0148400.978195.643245.20LC
Ground parrotPezoporus wallicus1.1711.17    LC
Brehm's tiger parrotPsittacella brehmii1.9211.92    LC
Vasa parrotCoracopsis vasa29.061905.201099.764911.57LC
Black parrotCoracopsis nigra37.691324.89738.95229.90LC
Gray parrotPsittacus erithacus48.2647422.6619798.238828.75NT
Brown-necked parrotPoicephalus robustus36.003773.081728.15898.36LC
Jardine's parrotPoicephalus gulielmi20.202274.301186.81449.20LC
Brown-headed parrotPoicephalus cryptoxanthus16.201692.27636.61308.58LC
Niam-niam parrotPoicephalus crassus10.06210.06210.06210.06LC
Meyer's parrotPoicephalus meyeri31.022754.531508.05609.63LC
Rüppell's parrotPoicephalus rueppellii20.54495.23355.23215.23LC
Red-bellied parrotPoicephalus rufiventris22.231921.92657.49347.72LC
Senegal parrotPoicephalus senegalus27.167363.883616.601865.47LC
Hyacinth macawAnodorhynchus hyacinthinus54.2656812.5242218.2314121.77EN
Lear's macawAnodorhynchus leari43.571314.561117.86  CR
Spix's macawCyanopsitta spixii32.2296.18715.18320.21CR
Blue and yellow macawAra ararauna48.5221246.60129712.5527320.78LC
Blue-throated macawAra glaucogularis32.792312.551718.201218.66CR
Scarlet macawAra macao48.2613608.3689614.5918821.24LC
Green-winged macawAra chloroptera63.049819.5167014.4418019.19LC
Military macawAra militaris54.435818.5738514.1611020.12VU
Great green macawAra ambigua34.757810.735619.881624.83EN
Red-fronted macawAra rubrogenys36.212416.4814313.844219.77EN
Chestnut-fronted macawAra severus39.671355.738010.571319.80LC
Yellow-collared macawPrimolius auricollis25.211533.03689.58919.60LC
Blue-headed macawPrimolius couloni13.30213.30213.30213.30EN
Blue-winged macawPrimolius maracana24.95936.876114.482318.23NT
Red-bellied macawOrthopsittaca manilata9.72432.01166.89  LC
Red-shouldered macawDiopsittaca nobilis22.911572.515911.641518.98LC
Thick-billed parrotRhynchopsitta pachyrhyncha35.243596.2120215.604020.74EN
Golden conureGuaruba guarouba60.903734.5919014.103421.68EN
Blue-crowned conureAratinga acuticaudata22.49992.89428.81419.23LC
White-eyed conureAratinga leucophthalmus28.45932.282810.15623.35LC
Green conureAratinga holochlora21.06440.8987.96  LC
Hispaniolan conureAratinga chloroptera30.841418.231418.231318.23VU
Cuban conureAratinga euops14.71151.7967.63  VU
Finsch's conureAratinga finschi14.16114.16114.16  LC
Red-fronted conureAratinga wagleri24.86358.32308.32215.58LC
Mitred conureAratinga mitrata27.83933.45418.441127.83LC
Red-masked conureAratinga erythrogenys26.641084.40568.93221.02NT
Golden-capped conureAratinga auricapillus18.85256.73198.43118.85NT
Jandaya conureAratinga jandaya22.241651.92699.53719.98LC
Sun conureAratinga solstitialis29.705292.0720010.982318.98EN
Dusky-headed conureAratinga weddellii24.57125.3989.27124.57LC
Brown-throated conureAratinga pertinax19.73311.42108.58113.73LC
Olive-throated conureAratinga nana7.1252.0917.12  LC
Orange-fronted conureAratinga canicularis28.621310.87238.80223.42LC
Peach-fronted conureAratinga aurea15.341242.19256.58  LC
Cactus conureAratinga cactorum9.08156.26106.47  LC
Nanday conureNandayus nenday30.244113.391859.001920.79LC
Patagonian conureCyanoliseus patagonus34.124397.1129411.196218.56LC
Monk parakeetMyiopsitta monachus24.784553.762176.65522.24LC
Slender-billed conureEnicognathus leptorhynchus20.17233.87119.28  LC
Maroon-bellied conurePyrrhura frontalis17.42401.521311.05  LC
Green-cheeked conurePyrrhura molinae8.3438.2238.22  LC
Maroon-tailed conurePyrrhura melanura12.0531.24112.05  LC
Crimson-bellied conurePyrrhura perlata22.34217.41158.44  LC
Fiery-shouldered conurePyrrhura egregia12.16212.13212.13  LC
White-eared conurePyrrhura leucotis10.6126.57110.61  NT
Painted conurePyrrhura picta17.75770.571211.26  LC
Black-capped conurePyrrhura rupicola6.0960.0126.09  LC
Blue-throated conurePyrrhura cruentata20.382910.571716.85418.53VU
Barred parakeetBolborhynchus lineola6.0333.7316.03  LC
Andean parakeetBolborhynchus orbygnesius9.65282.2497.53  LC
Mexican parrotletForpus cyanopygius12.02356.37228.10  LC
Green-rumped parrotletForpus passerinus11.58222.4274.72  LC
Blue-winged parrotletForpus xanthopterygius27.90153.0379.16227.90LC
Spectacled parrotletForpus cospicillatus7.1224.1817.1217.12LC
Pacific parrotletForpus coelestis30.381451.27286.07224.26LC
Yellow-faced parrotletForpus xanthops10.50224.47126.18  VU
Plain parakeetBrotogeris tirica4.21241.7434.21  LC
White-winged parakeetBrotogeris versicolurus17.84891.88296.82  LC
Gray-cheeked parakeetBrotogeris pyrrhopterus13.78203.4898.03  EN
Orange-chinned parakeetBrotogeris jugularis22.79430.0457.05  LC
Tui parakeetBrotogeris sanctithomae15.1561.86210.01  LC
Black-capped parrotPionites melanocephala27.07963.404513.21820.71LC
White-bellied parrotPionites leucogaster23.14344.97265.79320.28LC
Pileated parrotPionopsitta pileata19.51298.27229.20119.51LC
Caica parrotPionopsitta caica28.24128.24128.24128.24LC
Blue-headed parrotPionus menstruus23.03793.07377.36118.90LC
Red-billed parrotPionus sordidus5.7032.8315.70  LC
Scaly-headed parrotPionus maximiliani23.86318.472110.25216.63LC
Plum-crowned parrotPionus tumultuosus13.7684.37411.29  LC
White-capped parrotPionus seniloides7.6017.6017.60  LC
White-crowned parrotPionus senilis13.45712.63413.02  LC
Bronze-winged parrotPionus chalcopterus18.98362.151315.23518.23LC
Dusky parrotPionus fuscus9.10161.5077.26  LC
Yellow-billed amazonAmazona collaria11.6177.9168.10  VU
Cuban amazonAmazona leucocephala30.832924.091657.772421.24NT
Hispaniolan amazonAmazona ventralis29.061173.61536.30114.15VU
Black-billed amazonAmazona agilis8.0028.0028.00  VU
Puerto Rican amazonAmazona vittata27.23631.50289.03  CR
Tucuman amazonAmazona tucumana26.191095.08665.411018.96NT
Red-spectacled amazonAmazona pretrei24.23181.26523.54423.69VU
White-fronted amazonAmazona albifrons35.241333.76648.76920.05LC
Yellow-lored amazonAmazona xantholora22.051112.331012.33122.05LC
Green-cheeked amazonAmazona viridigenalis39.453115.2418011.593320.68EN
Lilac-crowned amazonAmazona finschi30.731334.477411.131525.29VU
Red-lored amazonAmazona autumnalis37.841927.2812711.752618.44LC
Festive amazonAmazona festiva30.31359.662818.111121.10LC
Red-tailed amazonAmazona brasiliensis23.201618.891521.93822.34VU
Red-crowned amazonAmazona rhodocorytha26.943914.753215.371124.25EN
Blue-cheeked amazonAmazona dufresniana22.42158.43158.43619.48NT
Yellow-shouldered amazonAmazona barbadensis34.62468.773810.4589.46VU
Yellow-faced amazonAmazona xanthops24.73286.922311.90424.73NT
Blue-fronted amazonAmazona aestiva37.446465.3739510.227319.32LC
Yellow-crowned amazonAmazona ochrocephala34.454015.1824010.465017.75LC
Yellow-naped amazonAmazona auropalliata66.811857.9112411.453819.48LC
Yellow-headed amazonAmazona oratrix41.506203.3728510.485420.78EN
Orange-winged amazonAmazona amazonica39.022895.431748.443018.15LC
Scaly-naped amazonAmazona mercenaria6.5724.5216.57  LC
Mealy amazonAmazona farinosa42.901006.116210.401116.93LC
Vinaceous amazonAmazona vinacea26.94434.282212.15621.65VU
St Vincent amazonAmazona guildingii36.583217.302919.87334.70VU
St Lucia amazonAmazona versicolor38.752713.571719.92732.04VU
Red-necked amazonAmazona arausiaca29.65329.61229.63  VU
Hawk-headed parrotDeroptyus accipitrinus38.251636.5010113.571521.30LC
Purple-bellied parrotTriclaria malachitacea15.14125.8097.99  NT
Carolina parakeetConuropsis carolinensis15.55410.02315.03  EX

When further excluding species that do not have at least 20 individual records, 82 777 individuals from 199 species remained in the dataset used for the following lifespan analyses. Matched pairs analysis indicated that living adult median age is significantly different than median adult lifespan (age=11.12±4.79, lifespan=8.81±2.62; z97=2036.00, P<0.0001) with living adults today surviving longer on average than adults collectively over the last 200 years. Leastsquares regressions of log maximum lifespan and log median adult lifespan on log body mass revealed that mass was a significant predictor of maximum lifespan (F1,195=148.79, P<0.0001, R2=0.43; Fig. 1) median adult lifespan (F1,167=182.65, P<0.0001, R2=0.52) and median adult age (F1,96=71.11, P<0.0001, R2=0.43; supporting information Fig. S1) such that larger species were generally longer lived than smaller species.

Figure 1.

The regression of log of maximum lifespan on log of adult mass by parrot species with n=20 individuals. The slope of the fit line is 0.3215±0.0213.

Matched pairs analysis revealed that sex affected maximum lifespan (males=24.79±12.58, females=23.05±12.52; z196=3027.00, P<0.0001), median adult lifespan (males=9.12±3.19, females=8.93±3.09; z168=1671.50, P=0.0049) and median living adult age (males=11.37±5.00, females=11.15±4.91; z97=488.00, P=0.0490) with males living longer on average (Fig. 2).

Figure 2.

Histograms of lifespan by parrot species with n=20 individuals of female (a) maximum and (b) median adult lifespan and (c) median adult age, and of male (d) maximum and (e) median adult lifespan and (f) median adult age.

Least-squares regressions of log maximum lifespan on log median adult lifespan and log median adult age revealed that both were significant predictors of maximum lifespan (lifespan: F1,167=78.56, P<0.0001, R2=0.32; age: F1,96=42.75, P<0.0001, R2=0.31; Fig. 3). For both regressions the cockatoos were the most notable positive outliers.

Figure 3.

Regression of log of maximum lifespan on (a) log of median adult lifespan (slope=0.7975±0.0223) and (b) log of median adult age (slope=0.5759±0.0303). Points represent individual parrot species, plus signs indicate the species with a residual value >0.3, and asterisks indicate the species with a residual value <−0.3.

Lifespan trends for clades

Our selected clades of parrots differed in most lifespan parameters. A one-way ANOVA testing for differences among clades in the means of maximum lifespan (F5,77=13.27, P<0.0001), median adult lifespan (F5,69=15.65, P<0.0001) and median adult age (F5,37=112.14, P<0.0001) indicated that clades differed significantly in these parameters (Fig. 4). To assess whether these differences could be attributed to the size differences among clades, both clade and weight were run as factors in a GLM. There was no significant interaction between clade and weight for maximum lifespan (?5,71=5.35, P=0.3741); when this interaction term was removed and the GLM rerun, both clade (?5,68=32.07, P<0.0001), and weight (?1,68=21.66, P<0.0001), had a significant effect on maximum lifespan. In contrast, there was a significant interaction for median adult lifespan (?5,63=16.86, P=0.0048), but neither weight (?1,63=3.69, P=0.0547) nor clade (?5,63=5.71, P=0.3357) had significant effects with this interaction term in the model. There were insufficient degrees of freedom to run a GLM with an interaction for median adult age, but the effect of clade was significant (?5,36=101.88, P<0.0001) while that of weight was not (?1,36=0.56, P=0.4544). The Cacatua clade (cockatoos) showed the greatest mean of maximum lifespan at 50.78 years. In contrast, the Ara clade had the highest mean of median adult lifespan at 14.31 years. Overall, the Cacatua clade included some of the longest-lived individuals in the entire database, but out of the species held in captivity, 65% of them never had an individual live past 50 years old. Mean median adult lifespan for this clade was notably low in captivity (10.36 years), significantly less than the Ara clade, and did not differ from the Aratinga or Amazona clades whose mean maximum lifespans were 15–25 years less than that of the cockatoos. The median age of living birds is higher than the median lifespan of all birds for all six clades, but this increase is much less dramatic in the cockatoos than in Ara, Aratinga and Amazona (Fig. 4).

Figure 4.

Mean and se of (a) maximum lifespan, (b) median adult lifespan and (c) median adult age for major clades of parrots. Clades that do not share the same letter within the bar are significantly different based on a Tukey–Kramer HSD post hoc test.

Breeding parameters

Breeding parameters in captivity varied greatly across the 193 species for which breeding data was available (supporting information Table S2). When restricted to species with data for =5 individuals, the lowest median age at first breeding was 1.10 years for the orange-bellied parrot Neophema chrysogaster. The highest median age of last breeding was 19.75 years for the St Vincent amazon Amazona guildingii. The blue-eyed cockatoo Cacatua ophthalmica had the longest median breeding duration at 5.92 years. The longest median post-breeding duration was recorded at 5.16 years for Pesquet's parrot Psittrichas fulgidus (supporting information Table S2).

A one-way ANOVA testing for differences in the means of reproduction data among the six selected clades indicated that they differed in the median age of first breeding (F5,27=5.39, P=0.0015), median age of last breeding (F5,49=17.77, P<0.0001), median duration of active reproduction (F5,49=4.18, P=0.0031) and median duration of post-reproduction (F5,45=5.66, P=0.0004). Notably, the mean median duration of post-reproduction was longer than the mean median duration of active reproduction for Trichoglossus, Cacatua, Amazona and Platycercus (Fig. 5).

Figure 5.

Mean and se of (a) median age at first breeding, (b) median age at last breeding, (c) median duration of active breeding, (d) median duration of post-breeding for major clades of parrots. Clade bars that do not share the same letter are significantly different based on a Tukey–Kramer HSD post hoc test.

Life-history and IUCN status

After classifying species using the 2009 IUCN Red List, we found 68% of species were of Least Concern (LC), 10% were Near Threatened (NT), 11% were Vulnerable (VU), 7% were Endangered (EN) and 3% were Critically Endangered (CR; Table 2). One-way ANOVAs of lifespan and breeding parameters by IUCN status revealed that there was a detectable difference in adult median lifespan (F4,163=9.00, P<0.0001), median adult age (F4,93=6.44, P=0.0001), median age of last breeding (F4,125=3.55, P=0.0088) and median duration of active breeding (F4,125=4.65, P=0.0016) among the IUCN status groups. The species with VU, EN or CR (the classifications of highest threat) had greater average values for maximum lifespan, median adult lifespan, median age of last breeding and median duration of active breeding than did species classified as LC or NT.


Parrots have a reputation for being one of the longest-lived avian taxa (Prinzinger, 1993). This analysis of 260 species of captive parrots spanning the order Psittaciformes demonstrates that even closely related clades of parrots can differ dramatically in lifespan and duration of reproduction. While a few individual parrots have lived for nearly a century, the majority of parrots in captivity did not live much beyond two decades. Even when accounting for juvenile mortality, only 30% of the 260 species had median adult lifespans =10 years. Clearly, most captive parrots are not living as long as generally thought. However, we found that lifespan in captivity appears to be increasing, as the median age of living adult birds is significantly greater than the median lifespan of all birds in the database, despite the truncating effect on lifespan of considering only living birds. This increase is likely due to advances in animal husbandry and indicates that modern zoos have improved their care and maintenance of parrots. Below we discuss these general trends and their implications for the conservation of parrots.

Life-history trends in parrots

As found in a smaller analysis of parrot lifespan (Munshi-South & Wilkinson, 2006), we found that larger parrots had longer lifespans than smaller parrots. Even though parrots with a larger body mass generally lived longer than smaller bodied parrots, on average the difference in mean median adult lifespan and age was only about a decade within the six clades examined. When body mass was included as a covariate in the analysis, mass and clade had a significant interaction for median adult lifespan, suggesting the effect of body mass on median adult lifespan varied with different clades. In contrast, body mass and clade independently affect maximum lifespan.

Male parrots had statistically longer maximum and median lifespans than females. However, this difference was small (1.74 years longer max lifespan, 0.22 years longer median lifespan) and may not be biologically important. In general, there is no consistent pattern of sex differences in avian lifespans; some sources report that in many species of birds, males live longer than females (Holmes et al., 2003), but other sources cite females as the sex with the typically longer lifespan (Christe, Keller & Roulin, 2006).

Breeding parameter patterns for captive female parrots vary greatly across species. Some smaller species were able to breed before they were a year old, while many larger species still bred when they were past 40 years old (supporting information Table S2). Notably, several species also had very long post-breeding periods, and clade means of the median duration of active reproduction were similar to the median duration of the post-reproductive period. This similarity suggests that either (1) parrots are not being housed in situations where they can realize their breeding potential fully; (2) parrots have an unusually early reproductive senescence compared to other birds (Holmes et al., 2003); (3) female parrots have an extended lifespan in captivity relative to wild parrots and can live past the constraints on egg production (as seen in domestic quail; Vom Saal, Finch & Nelson, 1994). Housing is likely influencing the breeding data as not all zoo parrots have access to a sexually mature, opposite-sex conspecific in ideal breeding conditions, but this effect cannot be teased apart from the other factors until data on opportunity to breed is also recorded. While this is not always feasible, especially in monomorphic species, it would be beneficial for zoos to enter as much of these data as possible into ISIS, so the impact of biological factors could potentially be assessed.


While our analysis provides an important demonstration of the utility of the ISIS database for providing lifespan data on long-lived species, there are important caveats concerning the reliability of the data. The ISIS database is composed of data contributed by many different institutions that do not necessarily adhere to the same standards of accuracy, reliability, diligence and comprehensiveness in record keeping. While we tried to eliminate clearly erroneous records during our initial compilation of the data, some questionable values remain (e.g. the age at first breeding of 0.29 years from Cyanoramphus novaezelandiae, supporting information Table S2). Data accuracy can depend on the species, as parentage is harder to ascertain in group-living species than for species housed in pairs. In many cases, individual records may also represent an incomplete account of the entire lifespan due to transfers of animals in and out of ISIS member institutions. Overall, we suggest that the greatest care be exercised in generalizing from breeding data, as captive breeding is dependent on opportunities provided by housing arrangements and thus most subject to biases introduced by captivity. Renewed commitment of all ISIS members to record keeping protocols would improve the value of this large database for species maintenance, reproduction and conservation. A more fundamental issue is that ISIS data are from captive animals. While captive animals rarely suffer levels of predation and starvation seen in wild populations, they may experience higher rates of inbreeding, unusual social group composition and captive conditions that produce physical and psychological stress (Meehan & Mench, 2006). It is difficult to assess the relative importance of these factors, but there are some indications that lifespan data from captive animals are a generally reliable predictor of lifespan in the wild (Ricklefs, 2000; Wasser & Sherman, 2010).

Conservation implications

This taxon-wide analysis of parrot lifespan and breeding parameters has several implications for conservation. First, survival in captivity should be taken into account when deciding which species to propagate. For example, the swift parrot Lathamus discolor had low residuals in the maximum lifespan on median adult lifespan regression (supporting information Table S3), meaning that many individuals of that species live nearly as long as the oldest surviving members. In contrast, the cockatoos had the highest residuals, and patterns in lifespan data that suggest while cockatoos have the biological potential to live for a very long time, few individuals are realizing that potential in captivity. We suggest that in the short term, zoos focus resources on propagating endangered species that fare well in captivity in order to create populations for potential reintroductions. International or regional studbooks should be created for the species that fit these requirements, which includes the swift parrot L. discolor, golden-shouldered parrot Psephotus chrysopterygius and sun conure Aratinga solstitialis. Long-term goals should include research aimed at improving husbandry and welfare so that endangered species that currently do not survive well in captivity, such as some cockatoos, can become better candidates for captive propagation programs.

Second, our data are the most comprehensive to date regarding lifespan and breeding in parrots. Such data are critical for parameterizing population viability models for wild populations. It is difficult to compare our captive data to data from wild populations, as the life-history traits of interest have been studied for relatively few species over a limited scope of time in comparison to parrot lifespan and reproduction. The majority of these studies estimate survival rates or fecundity (Saunders, 1982; Buckland et al., 1983; Rowley, 1983; Powlesland et al., 1992; Sandercock et al., 2000; Heinsohn & Legge, 2003; Murphy et al., 2003; Renton & Salinas-Melgoza, 2004; Beissinger et al., 2008; Koenig, 2008). A study on wild orange-bellied parrots reported life-history measures comparable to our captive data (Holdsworth, Dettmann & Baker, in press). Furthermore, two of the general trends we detected have particular importance for the viability of wild parrot populations, namely the shorter median lifespans than generally considered, and the long periods of post-reproductive lifespans. Taken together, these trends suggest that wild populations may be more vulnerable to rapid declines than previously thought.

Third, our results suggest that the suitability of older individuals for captive breeding should be carefully assessed. Many species in our dataset exhibited long post-breeding durations (see supporting information Fig. S2 and Table S2); it is not clear whether this phenomenon also occurs in wild parrots or is an artifact of captive conditions. Efforts to house pairs together could potentially increase the duration of active breeding and thereby maximize their value for conservation. On the other hand, if these long post-breeding durations are generally characteristic of parrot life-history, then many individuals will be surplus animals for as long a period as they were contributing active breeders. If true, this trend would put additional pressure on TAGs to refine their prioritization efforts.

Fourth, these data on average lifespan and breeding parameters may be used by TAGs as a rough guide for predicting future endangerment of species and proactively planning captive management priorities. We found that larger-bodied species that lived longer and bred later in life tended to be more threatened according to IUCN classifications. These trends suggest that TAGs should add lifespan and breeding measures to their existing criteria of number of individuals in captivity and IUCN status (AZA, 2007) in prioritizing the management of captive parrot populations for conservation.

Finally, this study demonstrates the general value and utility of the ISIS database and provides a baseline for demographic comparisons with wild populations. Even though caution must be exercised, ISIS provides a tremendous source of unrivaled information which can be used to parameterize population viability models for wild populations and adaptively manage captive populations according to conservation priorities.


We thank Christine Dahlin for statistical advice, Breanne Cordier and Aaron Hobson for assistance with data organization and Nadine Lamberski of the San Diego Zoo and Wild Animal Park for sponsoring our research request to ISIS. Funding for this research was provided by National Institutes of Health grant S06 GM008136 and National Science Foundation grant IOS-0725032 to T.F.W. This study was made possible by the dedicated record keeping of the staff members of ISIS and its member institutions.