Intraspecific Thievery in the Ant Ectatomma ruidum is Mediated by Food Availability

Authors

  • Benoit Guénard,

    Corresponding author
    1. Department of Biology and the Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC, U.S.A
    • Okinawa Institute of Science and Technology, Okinawa, Japan
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  • Terrence P. McGlynn

    1. Department of Biology, California State University, Dominguez Hills, CA, U.S.A
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Corresponding author; e-mail: zeroben@gmail.com

Abstract

Animals modify their foraging strategies in response to environmental changes that affect foraging performance. In some species, cleptobiosis represents an alternative strategy for resource access. The environmental factors that favor the incidence or prevalence of cleptobiosis, however, are poorly described. The cleptobiotic Neotropical ant Ectatomma ruidum is characterized by a high frequency of thievery behavior, a specific type of intraspecific cleptobiosis, in which specialized thief workers insinuate themselves into nests of neighboring colonies and intercept food items brought into these nests. Here, we evaluate how colonies adjust thievery behavior in response to food availability. We supplemented food availability and measured how the incidence and intensity of thievery responded to resource availability. We found that the incidence and intensity of thievery decline in response to supplemental food, suggesting that thievery behavior is a response to resource limitation at the population scale. This finding indicates that the phenomenon of intraspecific thievery, although a rare strategy in among colonies of social animals, is a viable alternative foraging tactic in the context of competition and food limitation.

Resumen

Los animales cambian sus estrategias de forraje respondiendo a los cambios del ambiente que afectan su modo de rebuscar su alimentación. En algunas especies, la cleptobiosis representa una maniobra alternativa para obteneer los mismos recursos. Sinembargo, los factores medioambientales que favorecen la incidencia o el predomino de la cleptobiosis estan muy pobremente explicados. La hormiga cleptobiotica Neotropical Ectatomma ruidum es caracterizada por una alta frecuencia de una conducta inclinada al robo, tipo especial de la cleptobiosis intraespecifica, el cual los obreros cleptomanos se infiltran en los nidos de las colonias lindantes y se apoderan de los articulos alimenticios traidos a estos lugares. A continuación evaluamos el como las colonias se acomodan a la conducta cleptomana segun la disponibilidad del alimento.Complementamos el alimento disponible y medimos como la ocurrencia e intensidad del robo respondia a la disponibilidad del alimento. Encontramos que la ocurrencia y la intensidad del robo disminuya de acuerdo con el aumento de alimento disponible, sugiriendo que el comportamiento cleptomano es una respuesta a la riqueza limitada de recursos en la escala poblacional. Este descubrimiento indica que el fenomeno de latrocinio intraespecifico, aunque una rara estrategia entre las colonias de animales sociables, es una tactica viable como alternativa en los distintos modos de forrejear alimento en el tratado de competencia y limite alimenticio.

Ancillary