FISHBIO: Fisheries research, monitoring, and conservation

Big gulp

March 29, 2013

It’s easy to find evidence that gulls can be aggressive foragers. Anyone who has watched a flock of gulls descend on food scraps, creating a feathered flurry of squawking and bickering, can attest to the voraciousness of these seabirds. While able to ingest seemingly large items (like a stolen sandwich) in the blink of an eye, it sometimes appears that a gull’s eyes are bigger than its stomach. The sea star this gull tried to eat is clearly not an easy meal, at least not without being picked to pieces.

Though it may seem nearly impossible for a bird this size to squeeze such a large prey item down its gullet, various gulls have been documented ingesting whole seas stars in one gulp. They accomplish this feat by scarfing down two of the victim’s five arms simultaneously, then waiting for the sea star to relax its other arms for easier gulping. Gulls may also attempt to force the star into a shape more conducive to swallowing by bending its arms against rocks or other substrate. While gulls are clearly among the few natural predators (in addition to otters, crabs, and some species of fish) able to feed on these stiff intertidal echinoderms, it would be quite a stretch to claim that sea stars are a snack that goes down easily.

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invasive species, Wildlife

Frog legs

March 20, 2013

It looks a bit like a fish with legs, but this giant tadpole is well on its way to becoming a full-grown American bullfrog (Rana catesbeiana). Bullfrog tadpoles can grow to 15 cm in length, dwarfing the tadpoles of other frog species, and they can remain in this stage of their life cycle for up to 2 years. Larger tadpoles make for larger adults (see Frog pile), and this voracious predator is known for its aggressive appetite, which includes a taste for other frog species.

Many people in the United States consider bullfrogs themselves to be good eating, and several species of frogs are important food sources for people in other countries (see Frog to go). While amphibian populations around the world are suffering massive die-offs and serious population declines, the American bullfrog is a hardy invasive species that thrives in areas where people have introduced it. This East Coast native is now comfortably at home in California and other western states, and scientists have linked bullfrogs to the decline of many native frog populations (Snow and Witmer 2010).

Tags: Bullfrog, frog, invasive species, tadpole

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Wildlife

Cat in the grass

March 6, 2013

Wildlife watching can be like playing a game of “I spy.” If you spend enough time outdoors in California and keep a sharp lookout, you might be lucky enough to catch a glimpse of a tawny-eyed bobcat. This shy wild cat we spotted is a master at going unnoticed – and appears to have had its eye on us long before we noticed it. Bobcats (Lynx rufus) get their common name from their stubby tails. They have the largest range of any wild cat in North America, and can be found across almost the entire Untied States, unlike their close cousins the Canadian lynx (Lynx canadenses), which mostly thrive in snowy areas. Bobcats are strictly carnivores, preying mostly on small mammals like rabbits, gophers, and grounds squirrels—with an occasional deer if they’re lucky (Labisky and Boulay 1993). Hunting and trapping bobcats is legal in many states, including California. The total take of bobcats in California increased sharply by 51% between the 2010-11 and 2011-12 seasons, to 1,813 cats. This is the highest number of cats killed since 1995, mostly as the result of commercial trapping, according to the California Department of Fish and Wildlife, which has spurred some state legislators to call for a ban on commercial bobcat trapping in California and limiting harvest to recreational hunters.

Bobcats are territorial, and stake out areas called home ranges that they mark with scat, scent, and scraped trees. Males’ larger home ranges often overlap several smaller female home ranges, and bobcats in the northern U.S. tend to cover more ground than those in the south (Caso and Lopez Gonzalez 2008). Studying these home ranges is important because one of the biggest threats that bobcats face is habitat loss, which crowds the cats into smaller areas. While bobcats can be quite adaptable in living near urban areas, researchers have found that adult female bobcats in particular mostly stick to undeveloped land – presumably as safer haven to raise their kittens (Riley et al. 2003). Spotting an animal like a bobcat can be great reminder of the wildlife we share a our natural backyard with. We saw this bobcat basking in the sun on the banks of the Tuolumne River at (where else?) Bobcat Flat.

Tags: bobcat, Tuolumne River, Wildlife

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Wildlife

On the prowl…

November 23, 2012

If you spend time outdoors in the Sierra Nevada foothills during the fall, chances are you may stumble across male tarantulas wandering in search of a mate. California tarantulas are typically shy arachnids, spending most of their lives solitary in underground burrows. Male tarantulas mature after 7 years and emerge from their burrows in the fall to mate. Unfortunately for males, after mating they are either killed by the female or die naturally within a couple of months. Females, on the contrary, can live for 20-25 years. After mating the female will lay eggs in a silk cocoon in her burrow and guard the eggs until they hatch in six to seven weeks. Approximately a week after hatching, the young will disperse in search of their own burrow.

Tags: tarantulas

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Wildlife

A horny toad…

October 12, 2012

This intimidating looking creature is often referred to as the horny toad. However, it is actually not a toad or amphibian, but is a reptile. The more acceptable common name is the horned lizard. There are 13 species recognized in North America of which four species are found in California. We found this juvenile Blainville’s (coast) horned lizard (Phrynosoma blainvillii) in the Salinas Basin along the Central California Coast.

Like all reptiles, they depend primarily on their environment to control their body temperature. They are typically found in sandy areas with sparse vegetation, making them susceptible to predation. One of the most unique characteristics of the horned lizard is their defense mechanism. When threatened, they can inflate their bodies with air thereby making them larger and harder to swallow. However, they are also capable of spraying blood from the corners of their eyes to repel predators.

Tags: horned lizard

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Wildlife

Hoo’s got their eye on us?

August 17, 2012

When working out in the field we try to be on our best behavior because we never know who’s got their eye on us. Just last week we were out conducting snorkel surveys, which generally involve long periods of looking down, when we happened to look up to see two adult and two fledgling great horned owls keeping watch over us in a nearby tree. People don’t usually expect to spot an owl during the daytime, but if you look hard enough they can be found roosting in the upper canopy of trees. The great horned owl, named for the ear tufts that usually stick up on their head, is one of the most widespread and common owls in North America and can be found in boreal forest, desert, suburban and urban areas. So, when working outside don’t forget to look up, with any luck you might spot a great horned owl.

Tags: great horned owl

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Wildlife

Guard frog

November 25, 2011

As we approached one of our weir sites we found this Sierran Treefrog (Pseudacris sierra) keeping watch over our electronic fish monitoring equipment. Treefrogs are typically found living among shrubs and grass near water, so this is not the usual tree frog habitat. But, thanks to their large toe pads they can also be found high up in trees or even perched on a padlock. Nice to know we have help keeping an eye on things over the holiday weekend.

Tags: treefrog

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Wildlife

Not the fall migration you’re thinking of…

September 23, 2011

Today is the first day of fall in the northern hemisphere, and so it only seems appropriate to mention migration. Whether by birds, insects or fish, migration is a universal behavior within the animal kingdom. Monarch butterflies, like this one photographed a couple of day ago, travel up to 2,500 miles to over-winter in California and Mexico. Migrations are generally driven by the fact that resources on Earth fluctuate seasonally, causing some animals to travel in search of food or breeding grounds, as is the case for Pacific salmon.

For Pacific salmon, their fall migration results in the end of their lifecycle. After spending one to five years in the Pacific Ocean feeding and growing to adulthood, species like the Chinook salmon (Oncorhynchus tshawytscha) will travel hundreds of miles upriver to their natal spawning grounds. The process of sexual maturity begins in the ocean many months prior to entering freshwater to reproduce. Research has demonstrated that the timing of migration and breeding is controlled by genetics (Quinn 2005). This inherited drive to migrate great distances, and against many odds, is impressive to say the least. Whether you’re looking for salmon or butterflies, keep your eyes open for the fall migration.

Tags: salmon migration

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Wildlife

You can thank me later…

July 29, 2011

We tend not to give turkey vultures (Cathartes aura) much thought. Since they feed on carrion, particularly road kill, they have a negative association in the minds of the general public. However, turkey vultures, named for their resemblance to wild turkeys, are impressive and important creatures. This species ranges from Canada to the very southern tip of South America, with several sub-species. Unlike most other scavenger birds, turkey vultures rely on their keen sense of smell to locate their dinner (Snyder and Snyder 2006). In the 1980s David Houston, a researcher from the University of Glasgow, tested this hypothesis by hiding chicken carcasses around a tropical island in Panama. Houston (1986) found that recently killed chicken were difficult for the vultures to detect, day-old chickens were found efficiently, and rotten chickens were not consumed. . . Even a scavenger needs standards, right? Thus, turkey vultures can detect hidden carrion and consume it, before the meat is rotten. It may seem strange, but vultures are vital to the health of the ecosystem – they act as a natural clean up crew, preventing the spread of disease from infected carcasses. In Africa (CEPF 2005) and India (Markandya 2008) the recent decline in vultures has been noted as a significant concern for both ecosystem and human health.

In the Central Valley turkey vultures scavenge along rivers and play an essential role in converting salmon carcasses into a source of nitrogen for the riparian vegetation and nearby crops such as wine grapes (Merz and Moyle 2006). So, next time you sip a glass of wine, be sure to thank the California turkey vultures.

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Miscellaneous, Wildlife

Mess-o-crayfish

June 6, 2011

Crayfish are known by many nicknames, including mudbugs, yabbies, mudpuppies, crawfish and crawdads. Like crab, lobster, and prawn they are decapod (i.e. “ten-footed”) crustaceans with twenty body segments grouped into two main body parts, the cephalothorax and the abdomen. Many people associate crayfish with warm slow moving rivers, ponds and lakes, but they can also be found in cool, clear streams as shown in this photo of a Pacific Coast stream. Peeking below the surface we found a mass of crayfish wedged along the margin of a submerged log. Most crayfish are nocturnal, utilizing some form of shelter like a burrow, rock, or log to remain hidden during the day. Nocturnal organisms are essentially using a form of crypsis (the ability to avoid detection by other organisms) in order to elude predators. If you taste as good as a crayfish, it’s a good idea to remain concealed.

Photo source: FISHBIO

Tags: crayfish