In the biggest regional study of its variety to date, marine ecologist Michelle Staudinger and colleagues supply much better understanding of the feeding ecologies of two really uncommon sperm whale species in waters off the southeast U.S. coast, adding baseline data they say are vital as climate change, fishing and pollution alters the animals' environment and food sources.
"Understanding what resources support populations of these extremely uncommon animals is critical to conservation," Staudinger, adjunct assistant professor in environmental conservation at the University of Massachusetts Amherst, says of the pygmy and dwarf sperm whales she studied. "If there are changes in the environment or their prey, we can now hope to much better anticipate the potential impacts. There had been rather a knowledge gap about these animals, but this operate provides us an notion of their ecological niche and requirements in the present atmosphere."
For the investigation, which made use of two complementary approaches to characterize whale foraging ecology, Staudinger and colleagues at the University of North Carolina Wilmington (UNC) analyzed stomach contents collected by the marine mammal stranding network from 22 pygmy and nine dwarf sperm whales discovered dead on the mid-Atlantic coast between 1998 and 2011. Study outcomes seem in the April concern of Marine Mammal Science.
These whales in the genus Kogia feed almost totally on beaked squid, cephalopods whose bodies are digested in whale stomachs except for the tough beaks made of chitin, a fingernail-like substance. Staudinger explains, "All deceased stranded marine mammals are necropsied, and scientists save and evaluate the stomach contents. So the stranding network had a stockpile of stomachs collected over 13 years from two of the most commonly stranded whales along the southeast and mid-Atlantic coast."
She adds, "Here I have to confess that I have a kind of unusual capability I learned in earlier research: I can recognize cephalopod species by their beaks, a characteristic similar to birds. So when I heard about this study, I jumped at the opportunity to study these whales."
Some cephalopod species she couldn't recognize from her personal reference samples, the marine ecologist noted, "so I went to the Smithsonian Institution's collection, exactly where there are hundreds of species in collections of whalers and fishermen dating back to the 1800s."
Specifically, Staudinger and colleagues hoped to identify variations, if any, in ecological niches occupied by pygmy and dwarf sperm whales. These smaller sized cousins of the sperm whale had been as soon as thought to be a single species until contemporary analyses showed they are genetically distinct.
Beak evaluation from cephalopod remains showed the diet plan of pygmy sperm whales to be extra diverse than that of the dwarf species, the researchers report, and prey sizes had been slightly bigger for the pygmy than for the dwarf, but not statistically substantially so.
In the second analysis, they evaluated ratios of carbon and nitrogen isotopes in whale muscle samples, an indicator delivering information and facts on which habitats the whales had been feeding in. That is, the eco-zone (e.g., mesopelagic and bathypelagic) and approximate depths exactly where whales had been feeding and regardless of whether their diets contained prey higher on the meals chain such as fish, or lower such as small crustaceans. Staudinger says, "As far as we know this the very first time the isotopic signatures have been published for dwarf sperm whales."
She adds that isotopic tracer data suggest these two rare species, although not precisely the similar, showed no important differences in foraging parameters. "We discovered the ecologic niche of the two species is quite equivalent in U.S. Atlantic waters, which is constant with other global studies," Staudinger summarizes. "The pygmy sperm whale consumes a greater diversity and size of prey, which indicates they may possibly be diving deeper than dwarf sperm whales to feed, this tends to make sense due to the fact pygmy sperm whales grow to larger sizes than dwarf sperm whales, having said that, this could also be an artifact of little sample sizes."
This is vital information and facts, Staudinger says, simply because if these two species show no evidence of resource partitioning there are likely sufficient meals sources to assistance both their populations in the area. Though if sources shifted or became limiting, pygmy sperm whales would most likely have an advantage over dwarf sperm whales as they show proof of becoming capable to exploit a wider variety of meals sources and habitats.
In the future, Staudinger plans to expand her knowledge in deep-sea squid ecology by means of further research of marine mammals with UNC Wilmington, and a new investigation of cephalopod biodiversity on the Bear Seamount in the North Atlantic with the Smithsonian Institution, and the National Marine Fisheries Service National Systematics Laboratory.
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