On July 16th, 2018 we learned about

Spawning salmon found to indirectly influence the number of berry plants grown from seeds in bear scat

If you’re trying to grow more berries in your yard, you might want to check on the local salmon population. Fish might not seem like the most intuitive component of a healthy cloud or blueberry crop (ok, maybe salmonberries…) but researchers have put together a food chain that shows how everything from salmon to rodents helps plant life in places like southeastern Alaska. It all starts to make more sense when you consider the keystone ingredient in berry production, which is bear poop. Obviously.

While freshwater fish do end up eating food that doesn’t live in the water, the salmon are simply an attractive but imperfect food source in this ecosystem. As they migrate upstream to spawn the fish are famously snatched up by brown and black black bears attempting to fatten up for the winter. While the salmon the are not the only component of a bear’s diet, their population density does greatly influence how many bears can be supported in a specific area. If there are more fish to be eaten, more bears can gather to start eating the next link in this food chain, the berries.

Bear scat with berry seeds

Berries have long been a critical component of bears’ pre-hibernation diets. The sweet fruits offer a lot of nutritional and caloric value for a bear, but they also carry seeds that other organisms depend on. Those seeds generally pass through a bear’s digestive tract unscathed, turning the bear’s poop into a concentrated collection of rodent-ready berry seeds. Detailed observations, including motion-sensitive cameras tracking activity around bear droppings, found that a single poop carried enough seeds to feed a deer mouse for 91 days. Various species of mouse seem to be aware of these bear-processed buffets, and individual animals would often visit scat multiple times a day to get as many seeds as possible.

Because the bears create such a rich concentration of seeds in a single poo, many rodents will try to “scatter-hoard” excess seeds in the surrounding territory, burying them in various locations for safe keeping. Just like squirrels attempting to hide acorns over a wide range, some of these seeds are forgotten by the mice and voles that buried them, greatly increasing the odds that a new plant will germinate. So while it might seem like the bear poop could act as a potential fertilizer for a new berry plant, the unintentional gardening of rodents is what really helps more plants take root.

Many individual steps of this process may not seem surprising, but the whole chain of dependencies may change how conservation efforts are organized. There are many reasons to try to preserve any one of the species involved in this process, but a good understanding of how they interact demonstrates how complex and interdependent an ecosystem can really be, from fish to seeds saved from scat.

Source: Berry-gorging bears disperse seeds through scat and feed small mammals by Chris Branam, Phys.org

On July 9th, 2018 we learned about

Crows strike first against ravens, preempting the risk supposedly posed by their fellow corvids

No bird wants to see more corvids move into their neighborhood. Aside from the likelihood that a magpie, crow or raven would outsmart their feathered kin, these birds are also likely to prey on smaller birds and their eggs. As much as that may threaten an individual chicken or swallow, it turns out that the corvids don’t really make a dent in overall bird populations; birds that corvids don’t catch are equally likely to be captured by some other predator. Nonetheless, it seems that some corvids have taken their dangerous reputation to heart, which may be why they attack each other so vigorously when there’s a nest that might need defending.

Aggressively preventing predation

After analyzing reports from thousands of amateur observers, a pattern became clear in crow and raven interactions. Without any kind of prompt, many of these observers noted how crows would seek out and drive ravens away from their territory, even before the ravens had made any kind of threatening movements on their own. In fact, the interactions were so one-sided that researchers found that the American and Northwestern crows were the aggressors in 97 percent of these interactions. The smaller crows did seem to avoid one-on-one interactions, preferring to form small teams to harass the larger ravens.

The aggression was most likely tied to nesting. Crows were most aggressive during breeding season, although they started to ramp up their attacks in the preceding winter months as well. Researchers believe that this was likely to defend a chosen territory and nesting site, blocking the ravens from gaining a foothold or access to resources anywhere near the crows’ eventual nursery.

Safe and sound?

Unfortunately, the actual predation of young crows by ravens likely isn’t as conspicuous as a team of crows driving a raven away, and so it’s less clear how much of an impact the crows behavior makes. If the pattern for corvids versus non-corvids holds true, it would suggest that while the crows may succeed in saving their young from the ravens, there’s a good chance some other threat may balance out their numbers nonetheless.

Source: Crows are always the bullies when it comes to fighting with ravens, Science Daily

On July 1st, 2018 we learned about

Raccoons that forage on humans’ high-calorie foods are boosting their blood sugar to unhealthy levels

“Maybe we should make raccoon-healthy food and disguise it as cake before we put it in the compost?”

While many raccoons might appreciate my daughter’s idea, I’m guessing that most wildlife specialists would prefer we just feed raccoons less food. After a few more minutes of brain-storming, even my kids realized that stocking compost and trash bins with food tailored to a raccoon’s dietary needs wasn’t really the solution to a growing problem in urban areas: raccoons that feed on our leftovers are getting bigger and fatter on our high-calorie diets, just like we are.

Foraging on our sweet, fatty foods

Wild raccoons should be living on hearty, raw foods like fruit, nuts, eggs, bugs and crayfish. And to be fair, a compost bin is likely to have a decent assortment of those items, albeit with a lot of other processed foods that people tossed out. This essentially makes too many calories too easy for a hungry animal to get a hold of, which would likely lead to increased fight production and other changes in metabolism. To see if human diets were making an impact on raccoons’ health, biologists looked beyond anecdotal reports of ‘fat raccoons‘ and started collecting blood samples for analysis.

Blood samples of three populations of raccoons were compared to see if environmental conditions, specifically access to human leftovers, was making a difference in the animals’ blood sugar levels. As one might expect, rural raccoons had much lower levels of glycated serum proteins (GSP) which are commonly used to monitor glucose levels in diabetics. The elevated blood sugar of urban raccoons suggests that they could easily be at risk of developing diabetes, metabolic disorders, and of course becoming obese. The catch is that most wild raccoons don’t live long enough for these problems to develop thanks to other hazards, like being hit by cars. So unless the raccoons are getting so fat they can’t dodge traffic, they might have no reason to mind a bit of extra french fries and ranch dressing in their diet.

Who benefits from bigger raccoons?

That’s not to say that our high-calorie leftovers aren’t creating a problem though. There’s actually a chance that these calorie-rich foods are boosting raccoons’ size and reproduction rates, which could create more conflict with humans. A larger raccoon with more kits may be more likely to break into our trash, fight with pets, and possibly spread parasites and disease. So even if city-dwelling raccoons don’t mind putting on some extra weight, the people sharing the neighborhood might really want to keep their leftovers to themselves.

Source: Raccoons experiencing high blood sugar levels from eating our food by Brandie Weikle, CBC Radio-Canada

On June 14th, 2018 we learned about

To avoid interactions with humans, more animals are becoming increasingly active at night

Millions of years ago, tiny mammals faced overwhelming competition from dinosaurs of all shapes and sizes. To avoid being gobbled up by hungry raptors or crushed under a distracted stegosaur, our shrew-like ancestors had to find a safe niche in their ecosystem where they wouldn’t be directly at odds with the dominant animals of the Mesozoic era. Their solution was to become nocturnal, allowing them to minimize contact with dinosaurs while continuing to live in the same locations. Once those dinosaurs were wiped out, mammals diversified and enjoyed more time in the sun, becoming the dominant vertebrates on land in the shape of deer, dogs, bears and more. However, research indicates that many species are being pressed back into the shadows, avoiding contact with the latest form of world-dominating creatures— humans.

Hints of this development have been noted for years. Nepalese tigers (Panthera tigris tigris), for instance, were documented shifting to a nocturnal schedule back in 2012. Motion-triggered cameras were set up in various locations around the tigers’ habitat, revealing a clear pattern in when the tigers were active. In places with less human activity, the tigers traveled day and night, but areas frequented by humans reduced their daytime activity by at least six percent.

Daily activities after dark

These night-owl tigers were apparently part of a larger trend. At this point, 76 studies of 62 species have seen similar shifts in animals’ schedules. From lions to otters, creatures around the world seem to be starting their day at night to minimize any contact with humans. That contact doesn’t even need to be explicitly dangerous their interactions with humans. While avoiding hunters may seem obvious, the analysis found that animals are changing their behavior around seemingly innocuous activities, like day hikes on footpaths. As much as people try to take only photos and leave only footprints, even a footprint may make some of our furry friends think twice about their daily routines.

This obviously isn’t the only time humans have functioned as an environmental pressure on wildlife, but it still stings a bit to realize how far other species will go to avoid being around us. Egos aside, biologists actually see an upside to this strategy, which is that it might work. While it’s obviously going to be disruptive to ecosystems if creatures like lions are staying up later to find food, the lions will probably still be better off avoiding potentially dangerous interactions with humans. As some species have found, coming out after people have gone to bed can work pretty well, allowing them to live in closer proximity to human developments than would otherwise be possible. Basically, if this strategy kept our ancestors safe from millions of years of dinosaurs, it will hopefully offer some of our current kin a way to stay safe from us.

Source: Many animals are shifting from day to night to avoid people by Emiliano Rodriguez Mega, Phys.org

On April 26th, 2018 we learned about

Damaged teeth and bones provide details about the dining habits of predatory dinosaurs

Few animals would likely enjoy watching a Tyrannosaurus rex eat its dinner, but from the safe distance of 65 million years, it’s easy to find the giant predators’ table manners fascinating. Many studies have investigated the potential strength and speed of a T. rex based on its own skeleton, but to study what effect they had on their prey, you need to look at the damage they caused to other animals. Biting into prey isn’t a one-way street though, and so researchers have also been investigating the damage to carnivorous dinosaurs’ teeth to figure out how they handled meal time.

Tucking in to a Triceratops

Naturally, the best record of T. rex snacking habits is in Triceratops. Looking through specimens found in Montana’s Hell Creek Formation, researchers found 18 examples of damage from Tyrannosaurus predation. In each case, the damage to the Triceratops‘ bone showed no signs of healing, indicating that the animal was dead or rapidly dying when the bone was damaged. Many of the wounds were puncture and pull marks, similar to what was found in the prey of other theropods. However, Tyrannosaurs‘ strong, thick teeth let them do a fair amount of manipulation with their prey, particularly around Triceratops‘ frill. Despite being mostly bone and keratin with little meat to munch on, Triceratops frills often had puncture marks in them. When coupled with bite marks on the dinosaurs’ ball-and-socket neck joint, researchers realized that T. rex was probably biting these bones to remove the Triceratops‘ head entirely. This would have exposed a lot of nutritious muscle tissue, although apparently the predators made a point of nibbling on their prey’s face as well, as indicated by precise, delicate bite marks other parts of the skulls.

While T. rex was a large predator, it was no small feat to remove one of the largest heads in history. Smaller, younger tyrannosaurs not only lacked the brute strength to manipulate a five-foot skull, they lacked the right teeth as well. Until they matured, younger predators’ size and tooth shape would have greatly influenced how and what they could safely bite without running into trouble. This is indirectly demonstrated in a separate study of a variety of theropods, from smaller Troodons to bigger allosaurs.

Biting without breaking their teeth

Instead of focusing on damage found in the bones of prey, this study looked at the microwear in each predator’s teeth. Combined with a modeling approach called finite elements analysis, paleontologists were able to model how each species would have most likely interacted, or chomped, on its prey. A common thread became apparent across various theropods, which was that they would start a bite with a vertical puncture into their prey, then pull their head backwards, essentially dragging their teeth through their target. However, the target in question likely varied according to each species of predator, as some teeth seemed much more durable than others.

On one end of this spectrum, large theropods like Gorgosaurus could safely bite into just about everything you would imagine a 30-foot-long predator eating. The wear and tear on their teeth indicated that they were likely biting larger targets with tougher skin. Conversely, Troodon teeth probably couldn’t handle much strain without risking damage. To compensate for their more delicate denticles, they were probably trying to eat softer, smaller fare, possibly even targeting invertebrates to avoid biting too roughly into bone. While no dinosaur wanted to break a tooth, these specialized bites were probably helpful to these predators— to avoid hurting themselves, they’d like go after different types of prey, avoiding the need to compete directly for the same source of food. Even if their initial bites followed the same pattern, having reason to aim those bites at different targets would have allowed more of these predatory dinosaurs to coexist in the same ecosystem.

Source: How to eat a Triceratops by Matt Kaplan, Nature

On April 17th, 2018 we learned about

Mosquitoes let researchers indirectly monitor the movements of invasive pythons

Burmese pythons (Python bivittatus) often grow up to twelve-feet long, but they’re still surprisingly hard to find in the wild. This is bad enough for the prey these snakes want to ambush, but it’s created challenges for researchers tracking their activity as well, even in environments where these snakes aren’t supposed to live. Since the 1980s, failed pet-owners have been importing and releasing pythons in the Florida Everglades, harming the native wildlife in those swamps. Fortunately, one local species seems to be quite adept at locating pythons, which is why researchers are “recruiting” mosquitoes to help track the snakes.

Following snakes via swarming mosquitoes

Despite the mobility of an individual mosquito, they’re still easier to capture than a single Burmese python. The work starts with cardboard funnels and hand-held vacuum cleaners, but is then followed with DNA sequencing in the lab to see what species of animals the mosquitoes have been eating. When python DNA turns up, it lets researchers construct a map of where they’re moving, and possibly how they’re multiplying across the Florida swamps.

Since this work started in 2015, a few trends are already clear. Python populations have been growing, and expanding northward. At this point researchers don’t have a strict head-count on the snakes, but they know that there are enough to be making an impact on other species in the Everglades. Raccoons, for instance, have been getting eaten often enough that the turtle and alligator eggs they usually eat are hatching at unusually high rates.

Other types of tracking

If digging through mosquito stomachs seems too indirect, conservationists have a few other ways to follow invasive pythons. One option is to collect samples of dirt found near burrows, then dig through them for traces of python DNA. Each time a snake slithers by, it sheds a bit of DNA, eventually leaving enough to confirm activity in specific locations.

For something a bit more actionable, there’s the sentry snake program, conducted by the Conservancy of Southwest Florida. Male pythons are outfitted with radio trackers, then released back into the wild where they’ll hopefully find a mate, and possibly some friends. Once contact seems to be made, conservationists can raid the “aggregation” of snakes, capturing other males and any fertile female snakes that were fertilizing eggs. This method is rather labor intensive, but it has led to the removal of over 3,000 fertilized eggs from the Florida swamps before they had a chance to hatch.

Source: A UF researcher is tracking snakes using mosquitoes by Wyatt Schreiber, The Alligator

On April 15th, 2018 we learned about

Beyond bugs, mammals, birds and reptiles play big roles in the pollination of flowering plants

On paper, the tongue of a Pallas’ long-tongued bat (Glossophaga soricina) may sound a bit like something from a horror movie. The South American bat’s tongue is made of spongy, erectile tissue, allowing it to increase its length by 50 percent when engorged with blood. It’s covered in an array of tiny, densely-packed hairs, which then stand perpendicular to the tongue when fully extended, allowing it to better capture the fluids the bat devours to stay alive. In practice though, none of this seems very grotesque, because G. soricina only uses its tongue to lap up nectar out of flowers, placing this bat in a niche closer to a honeybee than a vampiric parasite.

Scientists studying pollinators have found that the importance of vertebrate pollinators like G. soricina may be widely underappreciated. For all the attention played to pollinating bees and butterflies, a large number of plant species largely depend on bigger critters like bats, mice and even lemurs to fertilize their flowers. These aren’t strictly fringe cases either, as some flowers have evolved to be highly specialized, and thus dependent on just the right species of mammal or bird to be able to reproduce.

Nectar-eating bats and birds

Among mammals, bats are the most common pollinators, sometimes accounting for 83 percent of fruit production in a geographic region. They’re known to pollinate close to 530 species of plants around the world, often in relatively exclusive arrangements. For example, the blue agave cactus (Agave tequilana) which is used to make tequila, only open their flowers at night in order to attract greater (Leptonycteris nivalis) and lesser (Leptonycteris yerbabuenae) long-nosed bats. These bats don’t have hairy tongues, but the hair on their bodies collect and spread pollen just like the fuzz on a bumble bee.

As the specialized beak and tongue of a hummingbird indicates, many species of our feathered friends also act as important pollinators. Beyond hummingbirds, 920 species of bird are known to spread pollen between flowers, and are estimated to account for five percent of flower fertilization where they live. In more isolated environments, like islands, that number goes up, with birds being responsible for at least ten percent of flower pollination.

No need to fly to flowers

The success of pollinating bees, bats and birds may suggest that flight is somehow necessary to pollinate a flower, but that’s not the case. Any animal that wants to sip nectar without destroying the flower that produced it can potentially act as a pollinator, which has lead to at least 85 plant species around the world that get regular visits from non-winged mammals. Mice, squirrels, possums and lemurs may all stick their noses into flowers enough to transport pollen. Even without fur, bluetail day geckos (Phelsuma cepediana) can act as pollinators, carrying sticky pollen on the tips of their noses.

As humans become more appreciative of how insect pollinators help keep ecosystems alive, this research shows that we need to also consider the bigger-bodied pollinators as well. As policies and even substitutes are being developed to help protect creatures we associate with plants humans grow on farms, we need to make sure the wider range of pollinators around the world are protected as well. After all, some of these pollinators have become very adept at their sticky, hairy line of work, and won’t be easily replaced.

Source: Lizards, mice, bats and other vertebrates are important pollinators too by Ecological Society of America, Phys.org

On April 8th, 2018 we learned about

Conservationists care for orphaned otters in oddly obscuring outfits

It’s so easy to fall in love with the adorable charm of a sea otter, possibly at the otter’s expense. As much as their cute faces and playful charisma may endear them to us, conservationists from the Monterey Bay Aquarium really don’t want the otters to reciprocate. Like all wild animals, sea otters stand a better chance at survival in the wild if they don’t learn to trust or rely on humans, even when orphaned at a young age. Young sea otters may need care, but only from surrogate otter mothers and people dressed as amorphous ninjas.

Finding the right role models

As their name implies, the surrogate mothers are female adult otters chosen to help raise orphaned pups. While they may never be released in the wild themselves, they ideally bond and help raise the pups, teaching tips on how to hunt, hide and live on their own. In some cases, the bond is strong enough that the surrogate will lunge, bite and squawk at human caregivers, helping the pup’s social development and reinforcing wariness towards humans, even if those humans mean the otters well.

Of course, identifying those humans may be tricky, as they dress like the aforementioned amorphous ninjas. To keep otter pups from learning to trust humans, any caregivers that hold, clean or feed the young pups dress in loose black smocks, clean lab gloves and a black welder’s mask. This way, if a young pup feels solace when being fed a bottle of “clamshake” from a human handler, they probably won’t ever see a similar handler again once released in the wild. They may grow up to find the sight of black garbage bags inexplicably comforting, but that should keep them from venturing into human-populated areas and developing dependencies on whichever people happen to be present. For the humans that are trained to help the orphaned otters, wearing the costume apparently doesn’t make the otters any less charming to care for.

Dressed for the otters’ success

These precautions may seem a bit extreme, but the success of the Monterey Bay Aquarium’s restoration projects indicates that they’re worth the effort. Since 1984, the Aquarium has been working to restore sea otter populations to their historic levels which had been reduced to tatters in the 18th and 19th centuries. At this point, the otters are no longer being hunted for their fur, but they have a ways to go before they can truly reclaim their historic range from Oregon to Baja Mexico. After raising and releasing 725 stranded otters, conservationists are seeing that the current challenges are based around a lack of kelp forests, making them venerable to sharks and making their preferred sea urchin diet less nutritious (as the urchins over-graze and then starve for more kelp.) It’s a rare scenario where an animal isn’t being directly threatened by human activity, not that they’d want a normal-looking human to get near them in the first place.

Source: Sea Otter Behavioral Changes and Adaptations in Contrasting Environments by Emily Loufek & Alicia Pereyra, Soundings

On April 1st, 2018 we learned about

Hunting regulations are reshaping how brown bears raise their young

Swedish brown bears are spending more and more time with their cubs, but it’s not thanks to needier offspring or any surge in maternal instincts. It’s actually been thanks to a process of elimination, as bears taking care of cubs can’t legally be hunted, meaning moms with an empty nest are more likely to be killed by humans. It’s one of a number of ways human activity is shaping bear behavior, as our activity puts pressure on some populations while protecting and encouraging others, possibly in ways we haven’t really considered.

Researchers investigated maternal behavior in Swedish brown bears (Ursus arctos) over the last 20 years to see how bans on hunting mother bears impacted their reproductive success. They originally assumed that hunting would push bears to wean their cubs at younger ages, trying to maximize their reproductive opportunities while they had the chance, similar to other animals that have been known to breed at younger ages when resources are scarce. However, the opposite proved true— bears that said goodbye to their cubs after one-and-a-half years were more likely to be hunted and removed from the overall population, while bears that stuck with their offspring for an additional year were more likely to survive. Over the course of two decades, the genes driving instincts for long-term parenting have had a chance to flourish, and these patient mothers are making up a larger and larger portion of bear populations.

An upside for offspring

The mother bears aren’t selfishly using their cubs as shields from hunting. A mother bear won’t mate until her cubs have moved on, and so male bears will attack offspring so the female will be more receptive to new suitors. Smaller cubs are obviously easier to attack, although bears that were on their own after a year and a half faced a 22 percent mortality rate.  Cubs that stayed with their mom were thus more successful, providing more benefits to bear family’s that stuck together. This may lead to some interesting consequences for non-hunting humans too, as mother bears in outside of Sweden have already been observed using human developments as safe havens from male bears that would harm cubs, meaning people may have to deal with an increasing number of urbanized bears as these trends continue.

These patterns all show how things like hunting regulations can make a big impact in ecosystems, even after hunting season has ended. While many governments impose regulations against hunting animals caring for young to try to keep populations stable, these rules may end up changing those populations as well. The number of bears in Sweden has been climbing, and more and more of those bears are sticking together in the safety of a family unit.

Source: Hunting regulation favors slow life histories in a large carnivore by Joanie Van de Walle, Gabriel Pigeon, Andreas Zedrosser, Jon E. Swenson & Fanie Pelletier, Nature Communications

On March 27th, 2018 we learned about

Providing food year-round promotes the growth of parasite-carrying bird populations

My son and I regularly grumble to each other about the people we see feeding ducks at a nearby park. It happens often enough that he doesn’t even bother repeating comments about how ducks shouldn’t be eating popcorn, and instead just sighs and rolls his eyes as well as a five-year-old can. While we’ve never handed out breadcrumbs to the local mallards, it turns out all these admonishments have been made from a bit of a glass house. Research is finding that other kinds of handouts, like the bird feeder we fill up on our porch, may also make a big impact on the health of migratory birds and potentially anyone that lives near them.

Feeders keep birds fat and infected

As we all learn at a young age, many bird species in North America migrate during the winter. When the weather gets colder, birds have a harder time finding enough food to eat, so they head south to warmer areas until spring. What’s less obvious to all of us is that those migrations strongly shape the bird’s ecology when they return home. Throughout the winter, migrating birds won’t be exposed to the same set of parasites that they encounter further north. This means that those parasite populations are weakened, making them less of a concern when the birds return. Those parasites also have to remain relatively gentle on their hosts, as a weaker, sicker bird is less likely to survive migrating in the first place, potentially cutting off the parasite’s lineage in the process.

Human-sourced food like bird feeders may be changing this balance. By making food available to bird year-round, a population of permanent residents may develop. Those birds continually interact with parasites, and can become more virulent in well-fed birds’ bodies. If that weren’t enough, the birds that never migrate are likely to lay claim to nesting sites before their traveling cousins’ return. Taken together, it means that birds that do still migrate will find themselves at a considerable disadvantage when they arrive in the spring.

Clean feeders in a migration-friendly yard

So what can you do if you don’t want to inadvertently train your local birds to stay home and strengthen strains of West Nile virus or other parasites? One option is try to plant as many native plants as you can, particularly looking for plants that co-evolved with your area’s native bird populations. While some conservationists advocate for the complete removal of bird feeders, a compromise might be to take steps to keep them clean. Make sure you regularly sweep out old food and husks, and clean feeders and bird baths to head off the transmission of pathogens. It won’t convince your local birds to head south, but it should help keep the birds that stay a bit healthier for the sake of those that still migrate each winter.

Source: Feeding wildlife can influence migration, spread of disease by University of Georgia, Phys.org