Biology Reference
In-Depth Information
of the model was incorrect; dung flies may trade-off feeding and mating, or danger
and mating, rather than simply maximizing rate of fertilization. A second possibility
is that the currency is correct but that the constraints have not been identified
correctly; perhaps males run out of energy reserves while in copula. Finally, the
whole idea of dung flies or other animals maximizing a currency may be incorrect.
Animals may simply not be that well tuned by the process of natural selection or they
may be lagging behind when some aspect of the environment changes (as we saw in
Chapter 1). The important point is that discrepancies between observed and predicted
behaviour can be used to inspire further studies of currencies, constraints and the
animal's environment, and so build up a better understanding of the animal's
decision making. Another important step is to analyse more thoroughly the
mechanisms underlying behavioural decisions.
Summary
Behaviour involves decision making (e.g. where to search, what to eat) which has costs
as well as benefits. Individuals should be designed by natural selection to maximize their
fitness. This idea can be used as a basis to formulate optimality models which specify
hypotheses concerning: (i) the
currency
for maximum benefit (e.g. maximize rate of
energy delivery to the nest, as in starlings, or rate of fertilizing eggs, as in dung flies) and
(ii) the
constraints
on the animal's performance (e.g. search and handling time, energy
costs, risks of predation). The emphasis of this approach is on quantitative, testable
predictions about the choices that will maximize fitness. Often the observed behaviour
deviates from the predictions of simple models: these discrepancies can then be used to
refine the model to provide a better understanding of costs, benefits, currencies and
constraints.
Foragers may minimize their risk of starvation by varying their risk-taking in response
to their own hunger and the mean and variability of food rewards from different choices
(juncos). Some animals store body fat as an insurance against hard times, while others
hoard food. Food storing birds have remarkable spatial memory and a specialized brain
(a relatively larger hippocampus than non-storers). Experiments with scrub jays reveal
that they have episodic-like memory (for what they store, where and when), modify
their storing in response to potential thieves and plan for the future.
Foragers often face a trade-off between feeding benefits and predation risk (fat stores
in great tits, prey choice by sticklebacks, habitat choice by bluegill sunfish).
Individuals may sample alternatives themselves to determine the most profitable
options, or they may use the behaviour of others as a cue (social learning), especially
when individual learning is costly (nine-spined sticklebacks). Chimpanzees and
meerkats learn foraging tricks from others in their group. Social learning may give rise
to local traditions (fish foraging or mating sites). Sometimes knowledgeable individuals
actively teach naïve individuals (ants, meerkats).
Both food storing and social learning (including teaching) may involve simple
behavioural mechanisms rather than complex cognition based on the recognition of
the intentions or knowledge of other individuals.
