Canadian Study Suggests Animal Offspring Are Larger When Dad Sticks Around

B.C. Study Finds Animal Offspring Larger when Father is Present

Burnaby Mountain, British Columbia – It may be that even the animal kingdom is better off with a traditional two-parent household if the latest study from Simon Fraser University is accurate.

According to study author Holly Kindsvater, a biological sciences researcher at the school, females produce larger offspring if the male remains with them during the gestation period. It stands to reason that if the male remains with the female, the two can assist in providing food and shelter which translate into more nutrients for the offspring.

These offspring are larger and stronger and have a better gene pool to pass on to their own offspring. While the study suggests that this is the benefit of having the male around, it is by no means an absolute rule.

The study noted deviations from the norm where a helpful male remained with its mate, but the female delivered smaller sized offspring. There were other times when the male was a slacker, and the female still delivered larger sized offspring.

According to the study abstract:

Female investment in offspring size and number has been observed to vary with the phenotype of their mate across diverse taxa. Recent theory motivated by these intriguing empirical patterns predicted both positive (differential allocation) and negative (reproductive compensation) effects of mating with a preferred male on female investment. These predictions, however, focused on total reproductive effort and did not distinguish between a response in offspring size and clutch size. Here, we model how specific paternal effects on fitness affect maternal allocation to offspring size and number. The specific mechanism by which males affect the fitness of females or their offspring determines whether and how females allocated differentially. Offspring size is predicted to increase when males benefit offspring survival, but decrease when males increase offspring growth rate. Clutch size is predicted to increase when males contribute to female resources (e.g. with a nuptial gift) and when males increase offspring growth rate. The predicted direction and magnitude of female responses vary with female age, but only when per-offspring paternal benefits decline with clutch size. We conclude that considering specific paternal effects on fitness in the context of maternal life-history trade-offs can help explain mixed empirical patterns of differential allocation and reproductive compensation.

Kindsvater believes that a helpful male mate can help promote the survival of smaller offspring. On the contrary, a female is better off having larger children if the deadbeat male is not around.

On The Web:

Animal offspring bigger if dad’s around, B.C. study finds
http://www.cbc.ca/news/technology/animal-offspring-bigger-if-dad-s-around-b-c-study-finds-1.2515233

Females allocate differentially to offspring size and number in response to male effects on female and offspring fitness
http://rspb.royalsocietypublishing.org/content/281/1779/20131981.short?rss=1