efficient and prudent predation might coincide in some cases -- predators select prey that are both the least productive and the most profitable

sometimes they might conflict -- prudent predation would then require restraint by a predator -- passing up easy prey in order to increase prey available later

which of the following observations suggest that wolves have evolved efficient predation or prudent predation or both?

• wolves kill a disproportionate number of old moose

• wolves kill a disproportionate number of young moose

• wolves hunt and kill both male and female moose equally

• in some studies, they have killed a somewhat greater proportion of males than females

let's consider how we might expect predation to evolve ...

do we expect alleles associated with efficient predation or with prudent predation to spread faster?

evolution by natural selection (as we discussed earlier) occurs whenever one allele spreads faster than another because of differences in age-specific survival and reproduction of phenotypes associated with those alleles

if individuals compete for limited food, those with restraints on obtaining food must reproduce and survive less well than those with no restraints -- as a consequence alleles associated with prudent predation decrease in a population and alleles associated with efficient predation spread

these changes happen in the short term, even if efficient predation results in less food in the long term

efficient predation is thus an evolutionarily stable strategy (ESS) in relation to prudent predation

a behavioral phenotype (often called a "strategy") is an ESS in relation to some alternative strategy when alleles associated with this strategy spread in a population even when they are frequent

in other words, a population of individuals with alleles for an Evolutionarily Stable Strategy cannot be invaded by individuals with alleles for the alternative strategy

notice that prudent predation does not spread in a population because it has short-term disadvantages for each individual -- even when there are long-term advantages for the population as a whole

prudent predation is thus a form of altruism -- altruism (as defined in evolutionary biology) occurs when behavior is disadvantageous in the short run (in terms of the spread of alleles) for the individual performing the behavior but advantageous for others

if efficient predation spreads in a population, can predators stay in evolutionary balance with their prey?

in this situation, predators and prey might enter an evolutionary arms race -- predators evolve increased efficiency in predation and prey evolve increased efficiency in escape or defense

mathematics of this situation suggests that ...

• one or the other might "win" the race and cause the extinction of the other (even if it becomes extinct soon afterwards itself)

• predator and prey might reach an equilibrium (if predator and prey encounter trade-offs that limit the evolution of efficiency)

• the advantage might oscillate between predator and prey (if predator and prey respond to each other with enough lag)

we consider a case for an evolutionary arms race next ...