Mate desertion

However, the decision of which mate deserts first and when creates varying reproductive outcomes for both males and females, leading to sexual conflict over parental investment.

In penduline tits (Remiz pendulinus), uniparental care is dominant, and either sex is capable of desertion during the egg laying period.

[3] As a result, in response, females have adopted two counter-adaptive behaviors that function to deceive the male regarding the clutch's progress.

Studies have shown a high correlation between length of time a male stays before deserting and number of days a female keeps her eggs buried.

[5] This relationship suggests that egg burial has evolved as an adaptive female behavior that attempts to control information males use to decide whether or not they should desert.

[2] In some cases, the second deserter may even take part in filial cannibalism, reaping its lost investment by eating its own offspring as nourishment.

[7] Lastly, a deserted individual may also attempt to trick another mate into helping provide care for its young, circumventing its cruel bind.

In response, the evolution of counter-adaptations that allow males to guard against female deception would be expected, as it is evolutionarily maladaptive for an organism to invest in unrelated offspring.

[8] For example, in species where mate desertion by males is prominent, females reproduce through internal fertilization and are thus responsible for carrying the eggs.

For instance, desertion by either sex is favored when remating opportunities are high, food for young is abundant, predation is low, current offspring are older, require little parental investment and are smaller than average size, and the deserter's contribution to parental care is low.

Females in weak physical condition are more likely to abandon offspring to complete migration, increasing breeding chances and opportunities for the following year.

Thus, mating strategies exhibited by snail kites are somewhat plastic, depending on varying environmental conditions.

[14] Game theory helps explain when parents are more or less likely to desert their offspring by taking into account the costs and benefits associated with these decisions.

John Lazarus developed a well-known game theory model for mate desertion, in which different outcomes are predicted using a payoff matrix.

For either the male or the female, the total payoff for the deserter (V1+M or V1+F) is less than the reproductive success obtained when both parents provide care (V2).

Consequently, in situations where the female's benefits of deserting are low, she will remain to raise her brood, maximizing her reproductive success.

Elaborate nest of a penduline tit
Cooper's hawk
Case 1. Because V 2 > V 1 +(M or F), neither parent gains any reproductive advantage by deserting their mate. For both parents, reproductive fitness equals V 2 . V represents reproductive success (see text for more details).
Case 2. At t 1 , the male benefits from deserting the brood because V 1 +M > V 2 . At this point, the female's fitness equals V 1 . At t 2 , the female benefits from deserting the brood because V 0 +F > V 1 . At this point, the male's fitness equals V 0 +M, and the female's fitness equals V 0 +F. V represents reproductive success (see text for more details).
Case 3. At t 1 , the male benefits from deserting the brood because V 1 +M > V 2 . At this point, the female's fitness equals V 1 . After this, the female cannot improve her fitness past V 1 by deserting, so she chooses to stay and provide care. V represents reproductive success (see text for more details).