Anti predator Behavior in Amphibian larvae

[Comrade Tortoise]

Costs and Life History Tradeoffs of Antipredator Strategies in Amphibians
By Benjamin Allen







Introduction

The predation risk at any given time is highest within the attack range of a predator, and is equal to the probability of a successful attack by said predator. If this is examined from the perspective of optimization, one would expect that a prey species will react primarily to this momentary predation risk. This is because by only responding when threats are imminent, they do not incur additional costs of defense, while still responding maximally to the predator (Fraker 2008). However, most of the time, the prey species is lacking the information necessary to completely optimize their strategy (Sih, Ziemba & Harding 2000). Because information is limited, the prey species is left with a choice. They can either incur a higher cost to defend themselves from predators, or they can incur the predation risk without mitigation. These are of course two extreme cases, but this sets up trade-offs between predation mitigation and the costs of anti-predator defense. Aquatic-breeding amphibians are interesting this respect. They possess complex life cycles that include ontogenic shifts in every aspect of their ecology from their habitat to position on the trophic web. They experience different predators and are under different selective pressures during their larval period than they do as adults. There are several different types of anti-predator strategies that amphibians engage in. Morphological defenses consist of things like increased tail depth for increased swimming performance (Lardner 2000) physiological defenses consist of secreted toxins (Brodie et al 1978), and behavioral defenses consist of tactics such as predator avoidance and alarm calls (Shelly and Werner 1990). There are also shifts in life history to minimize exposure to the highest predation risk. The trade-offs involved in all of these can lead to secondary effects on life history such as reduction in metamorph size and performance (Lardner 2000) and increases in larval period (Skelly 1992). It will be the anti-predator strategies of larval amphibians and subsequent life history effects that will the primary subject of this review. It will be done in a few stages: the first step will be to examine how amphibians assess predation risk; the second will be to evaluate modes of response to predation with a mind to what the costs of each mode could be; lastly an explicit look at the costs of predator-mitigation and the effects on life history traits.

Methods

In order to evaluate these questions, Web of Science was searched using the keywords “Tadpole+ Predatorâ€