Sea Otters, Alligators and Other Major Predators Are Reclaiming Historic Niches, Study Finds
Increasingly, large predators like mountain lions, alligators and killer whales are moving into ecosystems not traditionally associated with them. Mountain lions have been spotted prowling grasslands, alligators have been seen lounging on Florida beaches and killer whales have been spied swimming in freshwater rivers.
Many hypothesized that the animals were taking over new territories as their populations rebounded due to conservation efforts. But research published in Current Biology Monday suggests that they are actually taking back what was rightfully theirs.
The researchers looked specifically at sea otters on the Pacific coast of the U.S., who have expanded from kelp forests to estuaries, salt marshes and seagrass beds, and alligators in the Southeastern U.S., who have expanded from freshwater swamps into marine habitats like mangroves and seagrasses. The researchers argued, based on both the species' success in these "new" habitats when protected from human interference, as well as historical and archaeological evidence placing both sea otters and alligators in coastal marshes, that the predators were reconquering ground they had occupied before human activity drove them out.
"We can no longer chock up a large alligator on a beach or coral reef as an aberrant sighting," study co-author and Rachel Carson associate professor of Marine Conservation Biology at Duke's Nicholas School of the Environment Brian Silliman said in a Duke University press release. "It's not an outlier or short-term blip. It's the old norm, the way it used to be before we pushed these species onto their last legs in hard-to-reach refuges. Now, they are returning," he said.
The study's authors, who, in addition to Duke, came from the University of California Santa Cruz, the U.S. Geological Survey, the University of Florida and Kansas State University, suggested that the same might be true of other large predators moving into new niches, though more research needs to be conducted to confirm this hypothesis.
Examples of other potential reconquests include the movement of orangutans into disturbed forests, river otters into marine wetlands, canines like wolves and coyotes onto beaches and rocky shores and grey, harbor and harp seals from Arctic into subtropical waters.
Taken together, these movements also indicate that large predators are more adaptive than ecologists thought.
"The assumption, widely reinforced in both the scientific and popular media, is that these animals live where they live because they are habitat specialists. Alligators love swamps; sea otters do best in saltwater kelp forests; orangutans need undisturbed forests; marine mammals prefer polar waters. But this is based on studies and observations made while these populations were in sharp decline. Now that they are rebounding, they're surprising us by demonstrating how adaptable and cosmopolitan they really are," Silliman said in the press release.
This is good news for both predators and the ecosystems they are calling home again.
In the press release, Stillman used the example of sea otters' movement into estuaries. This habitat flexibility will help sea otters survive as kelp forests are threatened due to climate change. But it also helps estuaries, because the sea otters eat Dungeness crabs who otherwise eat too many of the sea slugs that prevent the estuaries from being overrun by epiphytic algae fertilized by urban and agricultural runoff.
The study's conclusion argued that its findings should be taken into consideration when determining conservation policy.
"As many of these consumers (and their habitats) are protected and managed by legislation, the habitats they are now re-colonizing (e.g., salt marshes) will also need to be considered as critical habitat in recovery plans. Indeed, as is the case with sea otters and alligators, these 'novel' ecosystems can potentially support much higher populations than current habitats listed as critical," the study's authors wrote.
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By Jason Bruck
Human actions have taken a steep toll on whales and dolphins. Some studies estimate that small whale abundance, which includes dolphins, has fallen 87% since 1980 and thousands of whales die from rope entanglement annually. But humans also cause less obvious harm. Researchers have found changes in the stress levels, reproductive health and respiratory health of these animals, but this valuable data is extremely hard to collect.
Researchers work with trained dolphins to learn more about their sensory abilities, seen here testing a dolphin's hearing. Jason Bruck / CC BY-ND
A Lot to Learn From Hormones<p>When sampling the blow, we are looking for hormones in mucus as these can be used to gauge psychological and physiological health. We are specifically interested in <a href="https://dx.doi.org/10.1371%2Fjournal.pone.0114062" target="_blank">hormones like cortisol</a> and <a href="https://doi.org/10.1016/j.ygcen.2018.04.003" target="_blank">progesterone</a>, which indicate stress levels and reproductive ability respectively, but can also help determine overall health.</p><p>Additionally, blow samples can detect <a href="https://dx.doi.org/10.1128%2FmSystems.00119-17" target="_blank">respiratory pathogens</a> in the lungs or nasal passages - blowholes evolved from noses after all.</p><p>This health analysis is especially important in areas with oil spills as the chemicals can cause hormonal problems that harm <a href="https://www.carmmha.org/investigating-how-oil-spills-affect-dolphins-and-whales/" target="_blank">development, metabolism and reproduction</a> in dolphins.</p><p>Hormone samples can provide scientists with valuable data, but collecting them from intelligent and unpredictable animals is challenging.</p>
Cetacean Collaborators<p>To build a drone that can stealthily collect spray from moving dolphins, we needed more data on their eyesight and hearing, and this is data that couldn't be collected in the wild nor simulated in a lab.</p><p>We worked with dolphins at facilities like Dolphin Quest in Bermuda, which provides guests opportunities to learn about dolphins while allowing <a href="https://dolphinquest.com/about-us/our-story/" target="_blank">scientists access to animals for noninvasive research</a>. Here the dolphins can swim away if they choose not to work with us, so we had to design the study like a game; the way a kindergarten teacher entertains a class. If the dolphins aren't interested, we don't get to do the science.</p><p>Over the course of hundreds of sessions, we sought to answer two questions: What can dolphins hear and what can they see around their heads?</p><p>To test dolphin hearing, we set up microphones and cameras to record dolphin behavior as we played drone noise in the air. We analyzed the responses to each noise – such as how many dolphins looked at the speaker – and used these as a proxy for their ability to hear the sounds.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="5f31daf07a652b8d64a093b993ee4e96"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/UjmQeH3vXHI?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Robodolphin doesn't look like a real dolphin, but it doesn't need to in order to train our drone pilots. C.J. Barton / Oklahoma State University / CC BY-ND<p>To build robodolphin, we worked with dolphins trained to "chuff" or sneeze on command to measure spray characteristics. We used high-speed photography to see the dolphins' breath as it moved through the air. Then we conducted high resolution CT scans of a dolphin head and 3D-printed a replica of a nasal passage.</p><p>Now, we have a complete robodolphin and are tweaking its sprays to be nearly identical to the real thing. This will allow us to determine how close we need to get to collect the samples, and therefore, how quiet our drone needs to be.</p>
The replica dolphin blowhole was designed from a scan of a real blowhole passage, and the spray it produces closely matches the real thing. Alvin Ngo, Mitch Ford and CJ Barton / Oklahoma State University / CC BY-ND
A Bit of Practice, Then Into the Wild<p>In the next few months, we will test flights over robodolphin with existing drones to determine the timing and strategy for collection. From there, we will fabricate a low-noise drone that can fly fast enough and with sufficient maneuverability to capture samples from wild dolphins. Like a video game, we will use the visual field data to develop approach trajectories to stay in the visual blindspots.</p><p>We plan to test our drones on a truck-mounted robodolphin moving down a runway, then using a boat to simulate realistic conditions. The next steps will involve ocean testing with dolphins trained for open ocean swimming. These tests will determine if our devices can catch and hold the hormones as the drone flies back to a researcher's boat.</p><p>Finally, we will deploy the system to collect data on wild dolphins. Our first goal is to test resident dolphins – animals that live on the coasts and deal directly with boat and oil industry noise – which will allow us to learn more about stress resulting from human impacts.</p><p>Those samples are a way off, but if all goes well we will have a specially built drone capable of flying long distances and capturing samples undetected in a few years. The samples collected will allow researchers to do better science with impact on the animals they study.</p>
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Billions worth of valuable metals such as gold, silver and copper were dumped or burned last year as electronic waste produced globally jumped to a record 53.6 million tons (Mt), or 7.3 kilogram per person, a UN report showed on Thursday.
Environmental and Health Hazard<p>Experts say e-waste, which is now the world's fastest-growing domestic waste stream, poses serious environmental and health risks.</p><p>Simply throwing away electronic items without ensuring they get properly recycled leads to the loss of key materials such as iron, copper and gold, which can otherwise be recovered and used as primary raw materials to make new equipment, thereby reducing greenhouse gas emissions from extraction and refinement of raw materials.</p><p>Refrigerants found in electronic equipment such as fridge and air conditioners also contribute to global warming. A total of 98 Mt of CO2-equivalents, or about 0.3% of global energy-related emissions, were released into the atmosphere in 2019 from discarded refrigerators and ACs that were not recycled properly, the report said.</p><p>E-waste contains several toxic additives or hazardous substances, such as mercury and brominated flame retardants (BFR), and simply burning it or throwing it away could lead to serious health issues. Several studies have linked unregulated recycling of e-waste to adverse birth outcomes like stillbirth and premature birth, damages to the human brain or nervous system and in some cases hearing loss and heart troubles.</p><p>"Informal and improper e-waste recycling is a major emerging hazard silently affecting our health and that of future generations. One in four children are dying from avoidable environmental exposures," said Maria Neira, director of the Environment, Climate Change and Health Department at the World Health Organization. "One in four children could be saved, if we take action to protect their health and ensure a safe environment."</p>
Europe Leads the Way<p>While most of the e-waste was generated in Asia (24.9 Mt) in 2019, Europe led the charts on a per person basis with 16.2 kg per capita, the report said.</p><p>But the continent also recorded the <a href="https://www.dw.com/en/the-eu-declares-war-on-e-waste/a-51108790" target="_blank">highest documented formal e-waste collection and recycling</a> rate at 42.5%, still below its target of 65%. Europe was well ahead of the others on this front. Asia ranked second with 11.7%.</p><p>The authors said while more that 70% of the world's population was covered by some form of e-waste policy or laws, not much was being done toward implementation and enforcement of the regulations to encourage the take-up of a collection and recycling infrastructure due to lack of investment and political motivation.</p><p>"You have to think about new economic systems," said Kühr.</p><p>One approach could be that consumers no longer buy the products, but only the service they offer. The device would remain the property of the maker, who would then have an interest in offering his customers the best service and the necessary equipment. The maker would also be interested in designing his products in such a way that they are easier to repair and easier to recycle, Kühr said.</p>
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