As conservationists work to recover endangered species populations, taking individuals that are maintained and protected under human care and reintroducing them into the wild, it becomes apparent that there is a great deal to learn about the science of species recovery. In a paper published in the recent edition of the Journal of Applied Ecology, a team of wildlife experts from San Diego Zoo Global, the U.S. Geological Survey, the U.S. Fish and Wildlife Service and the University of Nevada analyzed the effect of habitat quality on the survival and dispersal of released desert tortoises. Juvenile tortoises used in this study originated from eggs produced by females housed at the Desert Tortoise Conservation Center in Las Vegas. Ages ranged from 6 months to 4 years. The tortoises were translocated and monitored for one year, using radio tracking systems. "The goals of the study were to help re-establish populations of this threatened and declining species, and to understand better what critical resources on the landscape are associated with the ability of young tortoises to survive and thrive," said Ron Swaisgood, Ph.D., director of Applied Animal Ecology at San Diego Zoo Global. Tortoises released in habitat that included appropriate vegetation, rocks and the presence of animal burrows had lower mortality rates than those released in areas where land features offered fewer options for predator avoidance. "Burrows created by small mammals represent critical components of desert tortoise ecology," said Melia Nafus, Ph.D., a researcher for San Diego Zoo Global and lead author of the study. "Supporting healthy rodent populations through habitat management may improve juvenile desert tortoise survival and recruitment." Another interesting finding of the study was that tortoises released on rocky ground were less likely to disperse away from the release site. "This finding probably relates to the tortoise's dependence on rocky substrate, as camouflage to hide from predators," said tortoise expert and co-author Todd Esque, Ph.D., from the U.S. Geological Survey. "The U.S. Fish and Wildlife Service encourages research such as this because it provides vital knowledge that informs our policy and management decisions," stated study co-author Roy Averill-Murray, who heads the service's Desert Tortoise Recovery Office. "Now, we have better information when deciding which habitats to protect for desert tortoises, and where to attempt re-establishment of desert tortoise populations with future releases." Translocation of individuals back to the wild is one of many important tools that conservation biologists use to recover endangered and threatened species. "We view these translocations as a way to learn more about animals' habitat requirements, while also assisting directly with species recovery goals," said Ron Swaisgood.
In 1992, Ole Karsholt and Jan Pedersen started collecting bugs in light traps on the roof of the Natural History Museum of Denmark in Copenhagen. A quarter-million bugs later, their data on 1543 species of moths and beetles provides astounding evidence that the we don't need to wait for 2°C of warming before seeing significant effects of temperature change on the insect community. As might be predicted, the insect "specialists" -- bugs that eat only a single species of plant -- experience temperature changes more dramatically than generalists. "Earlier studies have confirmed that specialist species also respond rapidly to destruction of their habitats, so we are dealing with a very sensitive group of animals” according to postdoc Philip Francis Thomsen from the Center for GeoGenetics, one of the authors of the study published in the Journal of Animal Ecology. The nut weevil, Curculio nucum, a connoisseur of the hazel nut, visited the museum roof in the early years of the study but disappeared in later years. Its place was taken by the acorn weevil, Curculio glandium, suggesting that both species are moving northwards to find cooler domains. The data on other specialist species supported the hypothesis, showing increases in populations of hot-dwelling species and decreases in those that prefer cooler climes. Insects that feed only during the non-mobile larval stage were seen to range quite widely from the habitats of their infancy at least 10 km distant from the museum roof. The team succeeded to register seven moth species and two beetles which had not previously been on record as inhabiting Denmark, including the Asian lady beetle (Harmonia axyridis) (pictured) which has now spread throughout the country and is considered an invasive species. The conversion of the data gained from the long-term voluntary monitoring project proves how invaluable such records can be. The authors hope their results will return funding for nature monitoring projects so that humanity does not have to depend on a spattering of committed enthusiasts. It seems like citizen scientists could lend a hand in the effort with a little political guidance, benefiting both the people involved and the state of scientific knowledge of our environment.
A new study published in the Journal of Animal Ecology found that migratory seabirds suffered negative repercussions when they had to spend more time rearing chicks, including decreased breeding success when they returned to the colony the following spring. The study artificially altered the length of the chick-rearing period for pairs of Manx shearwaters, giving new insights into the consequences for birds whose reproductive phase doesn't go to plan. All parent pairs involved in the study cared for their foster chicks until they were fully reared - often at their own expense. Lead author Dr Annette Fayet, of the Oxford Navigation Group in the University of Oxford's Department of Zoology, said: 'The results of this study provide evidence for carry-over effects on the subsequent migratory, wintering and breeding behaviour of birds.' Carry-over effects are the processes by which events in one breeding season may affect the outcome of the subsequent season. But the exact nature of these effects, as well as whether they affect other events in birds' annual cycles, such as migration and wintering, has been unclear. Dr Fayet said: 'Birds that had their chick-rearing period extended in our study delayed the start of their autumn migration and spent less time at the wintering grounds, and while they were there they spent less time resting. When they returned to the colony the following spring, they started breeding later, laid smaller eggs, reared lighter chicks - early, heavy chicks survive better - and overall had a lower breeding success. 'This suggests that the birds were in poorer condition after working harder during the experimental breeding season and shows the negative effects on both non-breeding and breeding behaviour in the year following the experiment.' Dr Fayet added: 'Conversely, birds that had a shortened breeding season in the experimental year started migration on time, spent more time resting and less time foraging at the wintering grounds, and had a similar breeding season to control birds the following year. 'Interestingly, this shows that "positive" carry-over effects occur but also that they may be less strong, or are shorter-lived, than "negative" ones.' The team conducted an experiment involving the Manx shearwater (Puffinus puffinus), a migratory bird with an average lifespan of around 30 years. Manx shearwaters nest in burrows on dense colonies along the British coast and embark on a journey of more than 8,000km to the Argentine Sea every autumn. Each year in spring they produce a single chick, which they generally feed for around 60 days. But the resources allocated by parents to feed their chick can vary: for example, factors such as food shortage, poor weather conditions, inexperience or late breeding - perhaps because of delayed migration or poor body condition - are likely to increase the energy expended during reproduction. This raises the possibility of birds being caught in a 'vicious cycle', where the carry-over effects of a difficult breeding season continue throughout the winter, making it harder for the birds to fully regain their body condition and thus have an easier breeding season the following year. In the study, the researchers swapped chicks between nests on the Manx shearwater colony of Skomer Island, Wales, artificially extending or shortening the chick-rearing period of 42 breeding pairs by around 25%. They then tracked the movement and behaviour of each adult with miniature geolocators, closely monitoring their breeding performance the following year (including laying date, egg mass, chick growth rate and breeding success). All pairs cared for their foster chick until normal fledging age, which resulted in a delayed start of migration for the pairs which had their chick-rearing period extended. Dr Fayet said: 'Controlled experiments like this one are rare but necessary to disentangle the complex mechanisms of carry-over effects and cost of reproduction in migratory birds. 'The results of this study are important because they reveal how carry-over effects can develop and affect animals throughout their annual cycle, and not just in terms of their breeding performance. They also help us understand how the decisions birds make regarding their life cycles - such as delaying migration to ensure their chicks are properly reared - are influenced by a complex relationship between individual body condition, external constraints, and current and future reproduction. 'Some 28% of seabird species are globally threatened, and numbers have dropped by 70% over the past 60 years. If all the events in a bird's annual cycle are linked, from breeding to migration and wintering, then any conservation measures to combat a species' decline must address these events together.' Dr Fayet added: 'However, we still have a lot to understand. For example, our study did not investigate whether carry-over effects affect the two sexes differently: do females, which have to produce the egg, pay a heavier price for being in a poor condition? Additionally, little is known about the duration of carry-over effects, which is likely to affect how long-lived animals optimise their life decisions.' Manx shearwaters do not recognise their chicks individually, and the breeding pairs used in this study were able to start migration no later than other naturally late breeders. Explore further: Hormones dictate when youngsters fly the nest: research More information: 'Carry-Over Effects on the Annual Cycle of a Migratory Seabird: an Experimental Study' Journal of Animal Ecology, Wednesday 31 August 2016. DOI: 10.1111/1365-2656.12580
With a final breath of air, I descend beneath the surface among swaying kelp and flying sea lions. I’m in search of a creature that has eluded me for many years. As a freediver, I’ve met the humbling gaze of a tiger shark and tossed around seaweed with playful wild spotted dolphins. But I’ve never faced the puckered lips and buggy eyes of the whimsical Mola mola — a fish that can reach the weight of an adult rhinoceros. Biologists have affectionately described Mola, or ocean sunfish, as a “a swimming head.” And while they seem to just float aimlessly at the surface, scientists are finding that these fish — which occupy a crucial evolutionary link in the fish family— are actually warming up after epic daily treks into deep water. A testament to this bizarre nature, a viral video of the sunfish circulated in September of 2015. The expletive-shouting Boston fisherman is unsure if he’s witnessing a baby whale or sea turtle, two seemingly dissimilar animals. He’s not the only one. These fish live off the California coast and around the world in temperate and tropical areas. But many people have never heard of them, let alone seen one. Mola mola are not endangered and not eaten in the United States. In fact, females can produce up to 300 million eggs, more than any other bony fish. But the hapless fish ends up tangled in fishing nets, as bycatch for more valuable target species. They make up the largest bycatch component (29 percent) in the California drift-gillnet swordfish fishery. So why does it matter if Mola mola are caught in mesh nets? Mola are pelagic, which means they live in the open ocean. Like humans, and many other fish, they have a bony internal skeleton. Sharks and rays, however, have a cartilaginous skeleton. According to some scientists, mola could provide a missing link to understand their open ocean neighbors animals, like sharks. “Sunfish are one of the most advanced bony fish, but they have a lot in common with cartilaginous fish. What they have in common may be adaptive to pelagic life and to study it may lead to solve evolution of pelagic species,” says Itsumi Nakamura, a biologist at the University of Tokyo. Mola have lost the calcium carbonate that makes their skeleton hard, so it’s more like a shark skeleton, says Christopher Lowe, a professor of marine biology at Cal State Long Beach State. Also like sharks, they lack a swim bladder that helps most bony fish stay afloat. Being lighter means using less energy, which is important when you are searching for hard to find and low calorie dinner items, common for deep-sea eaters, he says. Nakamura has studied the fish since 2009 and recently revealed mysteries of their strange behavior. Mola are often seen just lounging at the surface, he says. But new research published in the Journal of Animal Ecology from Nakamura and his team have found that mola actually make daily treks to the deep sea more than 2,600 feet beneath the surface — a place reserved for creatures like giant squid and diving sperm whales. Scientists have actually known mola dive deep for years. In fact, Lowe was one of the first scientists to track mola back in 2004. He speculated their diving behavior was related to regulating body temperature, but at the time scientists lacked the tools to test it, he says. Nakamura and his team “did a really nice job of demonstrating that, using appropriate new technology,” says Lowe. With the help of local fisherman in Funakoshi Bay, Nakamura’s team caught sunfish and outfitted them with thermometers, accelerometers, and video cameras. Though they can reach 2,600 feet, most trips throughout the day averaged between 350-600 feet. Mola returned to warm surface waters in between dives. This sunbathing behavior regulates their body temperature, and allows them to stay at depth longer, concludes Nakamura. It may also explain their large size. Larger sunfish can hunt longer and lose heat at slower rates than smaller ones, he says. So why journey to the dark and deep? They are eating jellyfish-like creatures, called siphonophores, says Nakamura. And it turns out, after observing the camera from one mola, they might be dining on the most nutritious part of the animals- their sex organs. “Of course I was surprised, because it is very novel that they eat only calorie rich parts of the jellyfish,” he says. Relaxing at the surface has another benefit for the sunfish; it’s a trip to the spa. Mola line up at cleaning stations, while smaller fish peck parasites from their body. For a more thorough cleaning, mola swim to the surface and seagulls jab through their flesh, feasting on parasitic worms. “They are a treasure trove for parasitologists,” says Lowe. Nakamura isn’t alone in his quest to understand the mola mola. Scientists are still trying to fill in the gaps for this under-studied species. This study demonstrates that mola are temperature sensitive, say Lowe. Global climate change and warming oceans will change their behavior and the distribution of their prey The question is, how? he asked. Tierney Thys has studied the mola for over 15 years and is researching everything from their vision and diving behavior, to pollutant levels. She recently published results from the first long-term tagging study of mola mola in the eastern Pacific in the Journal of Experimental Marine Biology and Ecology. They tagged 15 mola mola off the coast of southern California between 2003 and 2010. Of the 15 tagged individuals, four made dives greater than 1600 feet. It seems California mola are also diving deep. And last year, a lucky southern California native met a mola mola in the open sea. Ryan Brennan is the owner of a BMX bike show company, is a spearfisherman, and a freediver. He was headed 18 miles offshore on a foggy morning to go fishing with three friends. Still groggy from the 5:00 a.m. wake up call, he jumped into blue water. Like the Boston fisherman, Brennan had no idea what he was witnessing. “One of my first thoughts was, wow this one of the ugliest fish I have ever seen,” says Brennan. But Brennan spent time in the water, watching and observing the fish. And now, seeing the fish again is what he yearns to do the most, he says. “I saw the eyeball looking at me,” he says. “The more I looked into the animal, I realized it’s really beautiful.” Eventually the fish took off. And Brennan was surprised by how fast it moved. “They are unbelievably athletic, even though they don’t look that way,” says Lowe. The evidence is clear: the mola mola is more than just a lazy sun-bather. And while I have yet to meet one, I’ll continue weaving through kelp forests to find the “swimming head.” Bethany Augliere is a journalist in the science communication program at the University of California, Santa Cruz. She holds a master's degree in marine biology from Florida Atlantic University. For more of her work, visit her website or follow her on Twitter @BethanyAugliere.
Muller J.,Bavarian Forest National Park |
Stadler J.,Helmholtz Center for Environmental Research |
Brandl R.,Animal Ecology
Remote Sensing of Environment | Year: 2010
Whether diversity and composition of avian communities is determined primarily by responses of species to the floristic composition or to the structural characteristics of habitats has been an ongoing debate, at least since the publication of MacArthur and MacArthur (1961). This debate, however, has been hampered by two problems: 1) it is notoriously time consuming to measure the physiognomy of habitat, particularly in forests, and 2) rigorous statistical methods to predict the composition of bird assemblages from assemblages of plants have not been available. Here we use airborne laser scanning (lidar) to measure the habitat (vegetation) structure of a montane forest across large spatial extents with a very fine grain. Furthermore, we use predictive co-correspondence and canonical correspondence analyses to predict the composition of bird communities from the composition and structure of another community (i.e. plants). By using these new techniques, we show that the physiognomy of the vegetation is a significantly more powerful predictor of the composition of bird assemblages than plant species composition in the field and as well in the shrub/tree layer, both on a level of p < 0.001. Our results demonstrate that ecologists should consider remote sensing as a tool to improve the understanding of the variation of bird assemblages in space and time. Particularly in complex habitats, such as forests, lidar is a valuable and comparatively inexpensive tool to characterize the structure of the canopy even across large and rough terrain. © 2009 Elsevier Inc. All rights reserved. Source