In one day, a baby boy gained 200 pounds (90 kilograms) just from his mother’s milk. At this rate, it seems like he’ll be fully grown in no time. But this little guy has a long way to go. He’s a blue whale calf, and in five to 10 years, he’ll be the largest animal ever known to exist on Earth.
For now, he’ll continue to gain weight at this staggering rate and swim alongside his mother for another two years.
A new collaborative study suggests that characteristics like the slow maturation rates of blue whales may doom them to extinction. Already the International Union of Conservation of Nature (IUCN) deems them endangered.
One of the lead researchers of this study, Alison Boyer, an ecologist at the University of Tennessee, explains how she helped to create a statistical model to understand what factors make a species more likely to be “at risk.”
External pressures such as human impacts, together with intrinsic biological characteristics – like the number of births per year and body size at weaning – were used to try to predict the threat rankings across 125 species of marine mammals. One-quarter of these animals currently are listed as endangered.
The study showed that factors like a small geographic range or a slow reproductive rate are the best predictors of which species are struggling to survive. On the opposite end, species with large social groups, like bottlenose dolphins, tallied up as less at risk.
Developing a tool to help predict which species may be endangered is vital because 40 percent of all marine mammals are classified as data deficient by the IUCN, meaning that scientists just don’t know enough about the numbers of these elusive animals to predict their survival.
“The most exciting outcome of this study is that we were able to predict that 13 of the data-deficient mammals are likely to be endangered,” says Boyer.” This list includes Amazon River dolphins, which have found their way into local legends as spiritual enchanters. But with a slow reproductive rate, very small geographic distribution, and small social groups, they have many of the characteristics that predict them to be at a higher risk of becoming endangered.
After predicting which species are most likely to be at high risk, Boyer and her colleagues determined marine mammal hotspots – or danger zones – by identifying overlapping geographic ranges of the threatened species. Each hotspot contains six or more threatened marine mammals. Unfortunately, these regions often coincide with areas of high human impact (such as commercial fishing zones or shipping lanes). Blue whales often are killed when struck by large ships, and the Amazon River dolphin can drown from entanglement in fishermen’s nets.
So how can we help preserve these species?
One solution, says Boyer, is to create Marine Protected Areas (MPAs) at these crossroads of human and marine mammal activities. Similar to a national or state park, human activities would be limited within the boundaries of MPAs. In setting aside watery areas for the preservation of species, it’s important to note that the hotspots identified in this study span a mere 1.7 percent of all oceans.
Currently, the international community is looking at initiatives to designate 10 percent of the world’s oceans as MPAs by the year 2020. Boyer hopes her and her collaborators’ study can guide the placement of a portion of these new protected areas.
Even if enough ocean areas are set aside for these species to thrive, can they come back from their threatened status?
Very possibly. Boyer explains that marine scientists saw thrilling increases in numbers of humpback and gray whales after an international ban on commercial whaling. Sea otters and elephant seal populations also rebounded after certain protections were enacted.
Marine Protected Areas have real potential to protect and preserve the watery habitats of marine mammals, Boyer says. They may be necessary to ensure the survival of these graceful giants of the open oceans and the enchanting mystics of the Amazon.
Rachel Fovargue is a Ph.D. candidate at the University of Tennessee in the Department of Ecology & Evolutionary Biology.