1 dad + 1 mum + 2.4 children =
…well, a family, but just as this formula is pretty out-dated for most human societies, it turns out that lots of other species have complicated family lives too. Starting simple, there are species in which you see mum and dad raising their own young, for example great tits, emperor penguins and red foxes. But things start to get complicated when you add more individuals into the mix…
+ other families =
In group-living species, lots of families live together in one group, for example chimpanzees. Sometimes these groups can be huge – gelada baboons are regularly observed in groups of 350+ individuals!
+ individuals that don’t breed =
In communal breeding species, females share the costs of raising young by helping each other out. For example, in banded mongooses, females synchronise their pregnancies so that they all give birth on the same day. This means that pups are raised in one huge litter and all group members help to feed and look after them.
+ a pecking order =
In cooperative breeders, dominant individuals do all the breeding within a group whilst subordinate individuals are only allowed to help out with the rearing of young. Meerkats, African wild dogs and Seychelles warblers are all cooperative breeders, but however weird their family lives seem, there’s weirder still…
+ different body types =
In eusocial species, it is easy to tell which individuals breed and which don’t because they look totally different. Now, although they’re not exactly pretty to look at, the naked mole-rat is a great example of a eusocial species. The queen of a naked-mole rat colony is the only female that breeds and she can be twice as big as other colony members (and therefore twice as ugly). Although eusociality is rare in mammals, it is common in ants, bees and wasps. One amazing example is the army ant – in just a few days a single army ant queen can lay up to 300,000 eggs!
So, it’s not just humans that have complicated families. Next time you’re dreading Christmas with the rellies just think yourself lucky that you’re not playing host to a million army ants, or 75 naked mole-rats!
If you want to know more about the family lives of all creatures great and small, visit the ARKive website. I challenge you to find the only other species of eusocial mammal!
Bonnie Metherell, ARKive Media Researcher