Parents: To Care or Not to Care?
by Lisa Barrett
What kind of parental care did you or do you enjoy? Food, shelter, college tuition? How does this compare to parental care in non-human animals?
First of all, most animals do not receive any parental care at all. In other words, most animal parents do not invest in feeding, incubating, or defending their young after they are born. However, all animals do receive parental investment, in the very least by using time or energy in gamete production. This investment implies a tradeoff between how much investment parents can provide for a single current offspring and how much investment they can provide for the rest of the current offspring, or for future offspring. Salmon hatchlings, for example, will never meet their parents again (will never receive care), but before they hatch, their parents would have had to travel to a spawning location and perhaps prepare a nesting site (will have invested in their young). In fact, many species are this way, especially semelparous species, which only reproduce once in their lifetime (produce many offspring all at once), and usually die immediately after reproducing (think Charlotte from Charlotte’s Web).
So when would care be likely to evolve? In short, parents are selected to provide care for offspring that face adverse environmental conditions or predation. This includes high competition between conspecifics. For example, many male lions will never get to sire any cubs due to intense mating competition among males. Only the strongest and healthiest males will be successful with the ladies. In this case, it would benefit parents of male lions to provision, groom, and protect their young, as this would increase their likelihood of becoming successful, thereby passing on the parents’ genes. In animals whose offspring experience high predation rates, like crocodiles, it also benefits the parents to provide extra protection to their young.
Why do we see so much maternal care in animals? There is much variation in which sex provides care and how much care they provide across the animal kingdom. Most birds exhibit biparental care (both parents provide care) while most fish demonstrate paternal care (mostly male-biased care). The majority of mammals, though, display maternal care. This is likely due to the fact that male mammals have decreased certainty in their paternity compared to male fish or birds. Due to internal fertilization, mammalian males may be less sure that it was their sperm that ended up fertilizing the egg because sperm competition can occur (ever seen an episode of Maury?). In fish, which exhibit external fertilization, males can be pretty darn sure that they just fertilized a pile of eggs, and so those males are more likely to invest in those eggs by hanging around to provide care. Since birds are oviparous (lay eggs), there is also more opportunity for males to provide care, via incubating the eggs. Unlike how only female mammals can carry out gestation (and can multitask while doing so), leaving little for the male to help out with, incubation of bird eggs does not require the female, and so the male can help out a bit more!
These are just some explanations to shed light into how parental care in humans may be similar to or different from that of other animals!
Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press.