A few days ago, while taking an unplanned distraction break on Facebook, I came across a video of an enormous coconut crab attacking a red-footed booby. The footage was captured by a biologist studying crab behavior in the Chagos Archipelago in the middle of the Indian Ocean. On this trip he had already confirmed that the monstrous crustaceans snacked on large rats, but he never expected to watch one devour a full bird.
This video sent me on a research journey into other interesting meals discovered by animal researchers. Besides providing sensational headlines about what’s eating what, these studies help us understand everything from nutrient exchange to learned behavior. I’ve compiled a short list of observations and discoveries made in the past few months where researchers have used weird meals to understand complex phenomena. Warning: this might get gruesome!
Diner: Bottlenose Dolphins
On the Menu: Live Octopus
Swallowing an octopus is extremely dangerous, because the sucker-covered tentacles can latch onto the unsuspecting diner’s esophagus. According to some Australian marine biologists, bottlenose dolphins have developed a way to make sure their octopus supper goes all the way down. They observed dolphins systematically beating the octopus against the surface of the water to remove its head and make sure the arms are inactive. Some of the dolphins even tossed their food several meters into the air, which caused the cephalopod skin to break when it hit the water. This mostly happened in the winter and spring, which roughly aligns with when the octopuses breed and change colors, making them easier to spot. Of course, we’ve always known that dolphins were smart, but this is further evidence of dolphins developing systematic procedures and teaching each other. Along with their study, the team published some video footage with a short description of the dismembering procedure.
On the Menu: Sharks
The swamps and estuaries of Florida are a diverse environment where nothing is surprising. Except, of course, watching an alligator chomp down on a shark. That will always be cool. Sharks and alligators are usually separated by freshwater/saltwater divides, but in the mixed waters of an estuary, each one ventures a little farther out of its comfort zone. Alligators are opportunistic carnivores, meaning that while their diet usually consists of crustaceans and fish, they won’t hesitate to eat anything convenient, including small sharks. The study primarily focused on pumping the stomachs of alligators to learn about their diet, but it also examined the ecological impacts of the alligators moving between the saltier and fresher parts of the estuary. It reports that alligators play a key role in driving nutrients from the rich ocean water into the nutrient-lacking freshwater, nourishing entire ecosystems.
Diner: Kelp and Dolphin Gulls
On the Menu: Fur Seal Feces
Feces is, of course, a rich, healthy treat for animals bold enough to try it. Researchers from Chile observing fur seal populations noticed that the local gulls were particularly attracted to the pups’ feces. This was easily explained—the pups were highly prone to hookworm infections, resulting in ejected parasites and blood. However, the researchers also began noticing a distinctive pattern of infected perineal wounds on many of the pups. Apparently the gulls have grown too impatient for the meal and are instead searching for the feces right at its source—wounding the pups along the way. This relationship was probably commensal at one point, but through increased aggression of the birds, it has adversely affected the health of the pup population. The poor pups were already suffering endemic hookworms, but now the birds are leaving them with life-threatening infections and sores on their butts. The researchers are hesitant to intervene, though, because despite the apparent tragedy approaching the fur seals, human intervention can result in unpredictable, long-lasting effects on the whole ecosystem.
Diner: An entire ecosystem
On the menu: Drowned Wildebeests
The rain patterns of western Africa drive a massive migration of over a million wildebeests every year. Along the way, several thousand succumb to dangerous river crossings and drown. The carcasses provide a free meal for vultures and crocodiles, but according to some American ecologists, their positive impact on the river ecosystem lasts years beyond that. Initially, the soft tissue decomposition releases carbon, nitrogen and phosphorus into the water. The bones take much longer to break down, slowly releasing calcium and more phosphorus into the water. In the meantime, they’re covered with algae and bacteria, which provide a valuable food source for fish. This whole time, egg-laying bugs are thriving inside the decaying carcasses, and anything that eats the bugs has a continuous feast. Overall, the study estimates that one carcass will nourish the ecosystem for up to seven years.
- Nifong, James C., et al. (2017) Reciprocal Intraguild Predation between Alligator mississippiensis (American Alligator) and Elasmobranchii in the Southeastern United States. Southeastern Naturalist 16, 383-396.
- Seguel, M. et al. (2017) Kelp and dolphin gulls cause perineal wounds in South American fur seal pups (Arctocephalus australis) at Guafo Island, Chilean Patagonia. Royal Society Open Sci. 4.
- Sprogis, K.R., et al. (2017) Complex prey handling of octopus by bottlenose dolphins (Tursiops aduncus). Marine Mammal Science.
- Subalusky, A. et al. (2017) Annual mass drownings of the Serengeti wildebeest migration influence nutrient cycling and storage in the Mara River. Proceedings of the Nat. Acad. of Sci. 114, 7647-7652.
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