Animals & Wildlife Magazine

Nature's Remarkable Slowcoaches

By Frontiergap @FrontierGap

Nature's Remarkable Slowcoaches

On this week’s Frozen Planet, we heard about the amazing struggle many species have to endure just to make it to sexual maturity in the harsh conditions of the polar regions. One of the most striking was the incredible perseverance shown by the Arctic Woolly Bear Moth (Gynaephora groenlandica) found in Greenland and Canada, which has adapted to survive in temperatures as low as -70 degrees centigrade.
Unlike caterpillars from temperate regions which have a long summer to store up enough energy reserves to survive the metamorphosis into an adult moth, the Arctic Woolly Bears have only a small window in June when they can emerge onto the Tundra and graze available vegetation. This is not a sufficient period of time to allow them to mature. Consequently, when the ice and snow reappear, the Arctic Woolly Bears retreat into hibernation slowing and then partly suspending their metabolic processes, effectively leaving them frozen.
Though apparently dead, when spring returns, they miraculously thaw and continue with the considerable task of building their reserves. But for this resilient species, two summers is still not enough. In fact, it takes the Woolly Bears an incredible 14 years before they are ready to pupate, during which time they have spent 95% of their lives frozen. The adult moths emerge to see their last summer, when it is imperative that they find a mate and reproduce before the winter returns, a winter they will not survive.
This remarkable process of aestivation (dormancy) is an effective adaptation to the severe conditions found in the Arctic Circle. It allows Arctic Woolly Bear Moths to populate regions uninhabited by competing moth species and natural predators, though parasites do still pose a significant threat to the caterpillars.
Another species that also takes its time to reach reproductive maturity is the loggerhead sea turtle (Caretta caretta). An article published recently in Functional Ecology revealed that a female turtle will first lay eggs at the age of 45, which is much older than was previously assumed. Collecting definitive data on turtles has always been tricky owing to their long life cycles and nomadic lifestyles. However, this study took extensive measurements of young turtles, firstly as hatchlings at a nesting site in Florida, and again after their long journey to the Azores in the North Atlantic. With this data, the scientists were able to estimate their growth rate, which could be extrapolated to give the approximate ages of adult turtles laying eggs at the same nesting sites.
Loggerhead turtles are an endangered species and protected by the IUCN. Adult turtles are large enough to generally be safe from predation from marine species such as sharks, however human threats significantly contribute to turtle mortality (according to the 2009 status review of loggerheads by the Fisheries Service, drowning from entanglement in fishing gear is the turtles’ primary threat in the North Pacific). With the discovery of turtles slow maturation rates, it becomes apparent that with all the contemporary threats facing them, the chances of a turtle surviving to sexual maturity are significantly reduced. Unlike the Arctic Woolly Bear Moths, it seems that the turtles’ lifecycles and reproductive strategies are not best adapted to overcome the challenges they face.
By Claire Sherwood


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