August 23, 2022
… a little respect, please
This Sunday is Mother’s Day, a time to celebrate the people who do the world’s hardest job. Among sea creatures, there isn’t very much mothering or family life as people know them. Only the mammals – manatees, whales and dolphins – nurse and protect their children until they are well grown, but there’s still a lot of mothering going on and some of it is very hard work.
Millions of years of evolution have laid down three rules for species survival in the sea: Make the strongest babies possible, make a lot of them (in some cases, millions every year) and put them where they have the best chance of living to be juveniles. This can mean that the babies are abandoned at or before birth.
Many fish, including big roving hunters like snappers, jacks and groupers, spawn in crowds. This keeps the species’ gene pool well stirred. Spawning times are chosen to avoid peak feeding periods for other hunters, and spawning places are chosen so that the current, tide and waves will scatter the fertilized eggs, reducing the chance that they will all be eaten at once.
Mothers who stick closer to a fixed territory are more selective about their mates. Prospective fathers have to compete. For sharks, rays, moray eels and sea turtles this means a lot of chasing. Success depends on speed and endurance. Some others, including squid and octopus, usually back off their rivals with threatening poses and flashing colour displays. Actual fights do happen but they’re a waste of energy, and rare/
For some small fish, the choice of a mate comes down to who has the nicest house in the best neighbourhood. Male damselfish stake out a home territory, defend it aggressively, and may even “farm” the algae and soft corals they like to eat. At spawning time these males build rocky nests, and those who defend the best feeding territories and build the best nests have the most mothers coming to lay eggs.
Eggs that aren’t scattered need protection. Mother lobsters carry their eggs attached to their bodies until they are ready to hatch. (The closed lobster season allows time for this to happen.) Mother morays, sharks and rays hatch their eggs internally and give birth to little versions of themselves, ready to scatter and hunt for food – which may include any slow-moving brothers and sisters.
Although Jamaica’s crocodiles spend most of their time in or near water, they lay their eggs on land. A crocodile “nest” is a hole in a carefully built pile of mud, sand and dead vegetation near the water’s edge. It’s designed to keep the 50 or so large eggs at an even temperature through the 75-80 days until they hatch, and protect them from both flooding and drought. Mother crocs defend their nests fiercely against predators (including human poachers), and keep a watchful eye on their babies for a month or so after hatching.
Mother sea turtles also lay their eggs on land. They climb the beach where they were born, dig a pit for the eggs, and carefully fill in the pit so the eggs can be hatched by the heat of the sun and have some protection from being stolen by a dog, mongoose or human poacher. This is very hard work. Without the support of water, the turtle’s massive body is dead weight on legs not built for walking. Though most mother turtles do manage to nest more than once in a season, it’s not surprising that they only do it every two or three years.
The gold star for mother love goes to the octopus. A mother octopus lays up to half a million eggs on strings in a secure den, and stays with the eggs, guarding, cleaning and ventilating them, until they all hatch. While she is tending the eggs (up to five months if the water is cool), the octopus doesn’t feed and leaves the nest only to fend off intruders. Most females die, starved and exhausted, shortly after the last egg hatches.