What makes a species vulnerable to extinction? Comparative life-history traits of two sympatric snakes

  1. Jonathan K. Webb1,
  2. Barry W. Brook1,†,
  3. Richard Shine2

Article first published online: 23 MAY 2002

DOI: 10.1046/j.1440-1703.2002.00463.x

Issue

Ecological Research

Ecological Research

Volume 17, Issue 1, pages 59–67, January 2002

Additional Information

How to Cite

Webb, J. K., Brook, B. W. and Shine, R. (2002), What makes a species vulnerable to extinction? Comparative life-history traits of two sympatric snakes. Ecological Research, 17: 59–67. doi: 10.1046/j.1440-1703.2002.00463.x

Author Information

  1. 1

    Key Centre for Tropical Wildlife Management, Northern Territory University, Darwin 0909, Northern Territory, Australia and

  2. 2

    School of Biological Sciences, The University of Sydney, Sydney 2006, New South Wales, Australia

    **Author to whom all correspondence should be addressed. Email: barry.brook@ntu.edu.au

**Author to whom all correspondence should be addressed. Email: barry.brook@ntu.edu.au

Publication History

  1. Issue published online: 22 OCT 2002
  2. Article first published online: 23 MAY 2002

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Keywords:

  • Cryptophis nigrescens;
  • elasticity;
  • extinction;
  • Hoplocephalus bungaroides;
  • life history

Although it is well known that species vary in their vulnerability to extinction, the reasons are poorly understood. Theory predicts that long-lived species with ‘slow’ life histories (small litters, slow growth, late maturation) should be at greater risk than short-lived species with high potential rates of increase. This hypothesis was tested by comparing life-history traits of two species of sympatric, elapid snakes: the endangered broad-headed snake, Hoplocephalus bungaroides, and common small-eyed snake, Cryptophis nigrescens. From 1992 to 2000 a mark–recapture study of both species was undertaken in Morton National Park, south-eastern Australia, and this information was used to construct transition matrices for each species. The endangered H. bungaroides was found to mature late (6 years of age), had a high juvenile (54.7%) and adult (81.6%) survival rate, and a long generation length (10.4 years). In striking contrast, the common C. nigrescens matured early (within 3 years), had a lower juvenile (30.4%) and adult (74.4%) survival rate (but higher recruitment rate), and a substantially shorter generation length (5.9 years). Elasticity analyses revealed that H. bungaroides was considerably more sensitive to survival past the age of 2 years (68.6%) than C. nigrescens (37.4%). These results provide support for the hypothesis that species with slow life histories are more vulnerable to extinction.

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