Behavioral responses to HIREC


A key issue in the modern world is to understand variation in the ability of different individuals or species to cope with human-induced rapid environmental change (HIREC) including habitat change (loss, fragmentation, urbanization), exotic species, human harvesting, contaminants and climate change.  Some species are doing very poorly and are our species of conservation concern while others are doing so well that we consider them to be pests.  Often, apparently similar species (e.g., in the same genus) fall on opposite ends of this spectrum.  The challenge is to explain this variation.  For many animals, the initial behavioral response to HIREC is a key component of the species’ overall population response.  While there are a growing number of case studies on behavioral responses to HIREC, my lab’s contribution focuses on our efforts to develop a conceptual framework for organizing the results of these case studies and for generating a priori predictions.  Why do some individuals (species) respond well while others do not?  Our basic framework posits that past selection pressures have shaped behavioral tendencies (behavioral rules of thumb or cue-response systems) that determine how animals respond to novel situations.  Animals respond well if their past environments and post-HIREC environments are well matched, but respond poorly if HIREC has generated an evolutionary mismatch.  Our contribution has been to flesh out this basic idea with conceptual overview papers including literature reviews and first attempts at explicit theory (e.g., using signal detection theory or adaptive plasticity theory) on how an animal’s information about past and present environments (cue reliability, cue similarity), and costs of errors in past environments ought to affect response thresholds and patterns of behavioral plasticity in response to novel circumstances.  A graduate student, Dave Harris, a postdoc, Maud Ferrari, and I wrote a paper outlining our general framework (Sih, Ferrari & Harris 2011).  I have since sharpened that framework in 2 papers that are ‘in review’, including one on ecological traps with Bruce Robertson and Jenn Rehage.  In addition, we are applying the framework to specific issues; e.g. prey responses to novel predators and herbivore responses to novel host plants (see below).

a. Behavior and relative ability to cope with novel risks or resources.  Two recent papers (Sih et al. 2010a; Sih et al. 2011) outlined an integrative approach and reviewed literature on explaining variation in how organisms respond to and cope with novel risks or resources.  Why do some prey cope well with exotic predators, while others do not?  Why do some consumers adopt novel foods (e.g., crops, ornamental plants), but others do not? Understanding behavioral responses to novel cues that organisms have not seen in their evolutionary history requires a different framework than the optimality approach that dominates in behavioral ecology.  This work grows out of my earlier papers on costs and limits to plasticity (DeWitt, Sih & Wilson 1998; Gabriel et al. 2005; Sih & Gleeson 1995), as well as my earlier work on prey uncertainty and responses to risk (Sih 1992). It emphasizes the sensory and cognitive ecology of how organisms evaluate familiar and novel environments, and the role of evolutionary history in shaping sensory/cognitive systems.   The work on prey responses to novel predators has involved numerous collaborators.  The work on herbivore responses to novel plants is with Rick Karban, and two graduate students, Dave Harris and Ian Pearse.

Other incipient projects on behavioral responses to HIREC include: 1) collaborative work on the evolution of cues used to gauge seasonal timing (e.g. for onset of migration or onset of reproduction) and how variation in cue use relates to variation in adjustments to climate change; and 2) collaborative work on the evolution of the use of ‘win-stay, lose-switch’ strategy and how it might relate to variation in behavioral response to habitat change.