Bolsa Chica’s Furry Residents

By far the most visitors to the Bolsa Chica Ecological Reserve (BCER) are here to see birds. It’s a world class birding site and well deserves its worldwide reputation. But the dry land parts of the Reserve are also home to mammal species characteristic of our region and essential to its ecology.

What do mice, gophers, and ground squirrels have to do with the birds people come to watch? Well, they are what supports our many raptors, including some that most people don’t associate with rodents! If you could ask one of our stately, graceful, herons or egrets what they think of rodents, their response would probably be “Yummy!” The kites, harriers, falcons, hawks, and owls would certainly agree. And those same rodents also support the WILDEST residents of BCER, our snakes and coyotes!

Who are BCER’s mammals? First, it is necessary to remember that they come and go over time, and some that are “officially” listed as present have not been seen for decades. Let’s concentrate on those we may actually see!

Of course, we also get some mammalian travelers who visit BCER on occasion but aren’t often seen – bats appear after BCER hours, and seals, sea lions, and dolphins like to visit our seafood department every once in a while.

To preserve some natural order in this article, let us start at the bottom of the food chain and work upward! We’ll start small and go on to bigger, easier to spot critters—just don’t forget that the ESSENTIAL base of the system is the “little folks” at the bottom!

California Vole (Microtus californicus)

That’s right VOLE, not MOLE. Voles are a family of mouse-like animals. They are common in grasslands like our Lower Mesa. Unlike moles, insectivores that require damp soil which we normally don’t have, voles eat plants, especially growing grass seeds.

One way to tell a vole from a mouse is that voles have tails about half the length of mouse tails. Our species of vole is darker in color than mice. If you see a tiny, almost black creature scamper away from you in the grass, it is likely a vole.

We don’t have plagues of voles like some wheat-growing areas do, but they are common enough to provide quick snacks for most of our predators. White Tailed Kites are especially dependent on a healthy population of voles.

There have been true mice in our Native Plant Nursery, the Growing Space, but they were probably not native species, but the common European House Mouse.  However, more research is needed to know which mouse and rat species, native or not native, call Bolsa Chica home. Fine mesh cages around the plant growing tables and our friendly local snakes seem to have minimized their presence.

Botta’s Pocket Gopher (Thomomys bottae)

Here’s another common BCER mammal, but one seldom seen. That’s because they spend most of their time underground! Our species is the largest of its genus, shaped like a hamster but a bit larger. It is also the only pocket gopher that makes its underground tunnels with its front teeth as well as its strong front claws. A grown pocket gopher looks like a small beaver with BIG ugly “buck teeth” and a naked tail instead of the paddle tail of a beaver. Maybe it’s just as well that we usually only see the babies, who peek curiously at volunteers from burrow doors. Very cute, but every peek they take is dangerous! All our predators like fresh pocket gopher—snakes, raptors, including herons and egrets, and coyotes love ‘em. Safer underground!

The main way you can find pocket gophers is to look for the round “doors” of their colony burrows scattered over an area that has few woody plants. Pocket gophers eat roots, including the roots of the native perennials we plant as food for native animals – and sometimes they eat the plant right after we plant it. Turn your back and “Where’d my plant go?”  It went underground, roots first! Try someplace else…

These aren’t the gophers that golfers hate.  Those choose softer, moister soils for their root shopping as they can’t make their homes in our concrete-like soils.

Read more about these and other underground dwellers on our blog post Bolsa Chica Underground: Love and Hate

California Ground Squirrel (Otospermophilis beechi)

Probably our most visible mammal because their colonies are mainly along the trails that walkers, runners, and birders use—the edges of the Lower Mesa. They are sun lovers and come out when the sun does. They eat all kinds of seeds, grass sprouts, many of the same roots that pocket gophers eat, and sometimes insects like grasshoppers, and even roadkill! Our species is the largest of its genus and is found all over the West Coast from central Washington into Baja.

Most of our predators eat ground squirrels, especially their baby “pups.”  The squirrels live in complex deep burrows and are well-organized to protect themselves against one of their main predators, the Southern Pacific Rattlesnake. Adult squirrels fight vigorously against snakes and are immune to rattlesnake venom. They use their digging skills to blind and confuse the snake with dirt that they “dig” backward into its face!

They also are vigilant about other predators. When you see a squirrel on a fence post, up in a bush or tree, or on top of a tall weed, he is a male doing lookout duty. If he sees a predator approaching the colony, he will utter a high-pitched alarm squeak that sends his family underground!

Because squirrels live near our trails, they often become quite tame. Although they are cute, don’t approach or feed them! They don’t thrive on “people food,” tend to lose their survival skills, and also can carry some nasty communicable diseases. (And if you read signs, you’ll know it’s illegal to feed wildlife). They have one litter of 2 to 12 “pups” per year depending on food supply.

You can read even more fascinating facts on our blog post called Bolsa Chica Ground Squirrels

Desert or Audubon’s Cottontail (Silvilagus auduboni)

Cottontails are another visible mammal at BCER because they are active at several times of the day, depending on weather. They are most easily seen in the Coastal Sage Scrub areas along the Mesa Trail, especially in the denser areas around the Point. Cottontails are a common mammal in North America, found just about everywhere in the US that isn’t covered with concrete or blacktop—they are very adaptable and ours are well adapted to a desert climate.

One sign of that is that their ears and legs are longer than most other cottontail subspecies. Those larger ears, an adaptation to hot weather where they act as “radiators,” sometimes get them confused with the Black tailed Jack Rabbit (really a hare) that is listed as present at BCER but hasn’t been reliably identified here for years.  Another sign of the Desert Cottontail’s adaptation to our climate is their ability to metabolize part of their plant diet into water, a trait they share with ground squirrels.

Cottontails, unlike hares, live inside shallow burrows and raise their young there. They are a prime food for coyotes and large raptors, and even rattlers eat their young, so a snug underground shelter is one key their survival at BCER!

Striped Skunk (Mephitis mephitis)

We seldom see skunks at BCER because they are primarily nocturnal in our climate. They are a member of the weasel family (Mustelidae) and their closest relative in CA is the smaller Spotted Skunk, which isn’t found at BCER. The next closest is the Badger, which was once common in SoCal. It’s Spanish name “tejon” is on several prominent places. He is back again in the Eastern parts of the Orange County, and we wish he would return to BCER.

Skunks are omnivores who will eat fungi and ripe berries when available, but at BCER they specialize in small animals, including baby rodents, amphibians (few at BCER), bird and reptile eggs, and all sorts of bugs, grubs, and other larvae. BCER is probably too dry to support many skunks, but we do see them around the weir dam and the Warner Ave. walk bridge’s stone supports at early morning low tides, where they hunt among the rocks for crabs, which they seem to treat as big juicy bugs!

About the only enemies skunks have, besides cars and trucks, are Great Horned Owls, which snatch their kits at night when both owls and skunks are out hunting. Skunks are just another reason to leave your dog at home when you visit BCER – you’ll NEVER forget driving home with a “skunked” dog! Those black and white stripes read “BACK OFF!”

Northern Raccoon (Procyon lotor)

Raccoons don’t worry about mask-wearing—they’ve been doing it for thousands of years! Like skunks, raccoons are seldom seen at BCER because they are primarily nocturnal in our area. What we mostly see are their little handlike paw prints in the edges of the salt water and around our infrequent mud puddles in the Mesa Trail. Raccoons like to wash their meals in water, which is why suburbanites sometimes wonder how so much mud got on their swimming pool steps!

Raccoons are true omnivores that eat just about any small animal including bugs, snails, worms, frogs, and fish, as well as a wide variety of fruits, both native and domestic. They like human food, too, and their cunning little fingers are good at opening garbage bins. Don’t feed them! It can turn them into aggressive little panhandlers, liable to mug someone.

Raccoons are found across the Americas and in South Asia. Most of our raccoons live near the Pocket Marsh where there are two prerequisites for them: trees and fresh water. We don’t have a dense population because BCER has little of those. They need trees for their young to escape predators (mainly coyotes here) and they prefer to use hollow trees as dens, although they will den in rock crevices and small caves if there’s no usable trees.

They’re smart! Animal behaviorists have tested their intelligence with puzzles and mechanical locks that they must solve to get a food treat, and raccoons turned out to be better at these tasks than most “higher” primates. And they remembered the “tricks” of each puzzle for months!

The family that raccoons belong to, Procyonidae, was long thought to be related to bears because their dentition and nutrition resemble that of bears. But when modern genetic scientists analyzed their genome, they found them to be more closely related to canines (a shocking revelation to ‘coon hounds). However, dogs and raccoons don’t get along, and it is best to keep your dog away from them. They show bear-like ferocity and strength when they can’t retreat up a tree, although they are seldom aggressive if left alone.

Coyote (Canis latrans)

Coyotes are an “iconic” Western animal. People seem to love or hate them. At BCER we love them – by law and from our experience. It’s easy – they are very interesting creatures. Without them and their insatiable appetites we would be over-run with rodents that would eventually overwhelm the carrying capacity of the land, become malnourished and diseased and thus a menace to the rest of the environment, including their human neighbors.

Coyotes have been here a long time, evolving into desert animals from wolves after their parent species moved here from the Arctic. They are one of the most common fossils at La Brea, and key players in the mythology of most of the Native human cultures of the Americas, an important sacred ancestor, if often a very tricky one!

At BCER we see coyotes all over: out hunting rodents in the weeds and grasses on the Lower Mesa, along the saltwater looking for carrion, and stalking prey in the Coastal Sage Scrub. We seldom see more than a pair hunting in daylight hours, perhaps because they do most of their “family style” hunting in the twilights when rabbits feed most, and when we have left the Mesa. Coyotes mark their territory by leaving droppings on the trails they use to move quickly across their range. One sign that they occasionally leave the Reserve to forage in the suburbs is the presence of palm seeds in their scat. They digest the soft, sugary flesh around the seeds, but not the seeds themselves. Fortunately, the seeds don’t seem to germinate on the Reserve.

Coyotes are far-ranging and fast-moving animals. Leaving the Reserve to find food, mates, or new territory makes them vulnerable, especially to traffic, but also to toxic substances, unhealthy food, and canine diseases that they contract from domestic dogs. This vulnerability is countered by their adaptability, intelligence, and ability to increase their fertility when under population pressure.

Find more information and resources about Coyotes from the California Department of Fish and Wildlife’s Human-Wildlife Conflicts Toolkit: Coyote

Non-native mammals at BCER

Just as there are many non-native plants at the Reserve, there are also invasive species of mammals. We occasionally have rat damage at the Native Plant Growing Space, probably from the Eurasian rats that have naturalized seaside communities all over the planet: the Norway or Brown Rat and the Roof or Black Rat. Native California rats in our area favor oak woods and chapparal, which not available at BCER.

Another common invasive mammal in our area is the Virginia Opossum (Didelphis virginiana). These marsupials were introduced deliberately in the early 20^th Century from the Southeast US and have spread widely in the West. They are an interesting species that has survived since the dinosaurs, but not often seen at BCER; it may be too dry for their omnivorous diet, and the lack of trees denies opossums their primary refuge from predators – climbing out of reach. Their other main defenses, hissing and then “playing ‘possum,” just don’t work with coyotes!

Enjoy our mammals. They aren’t nearly as visible or colorful as our birds, but they also are an integral and essential part of the Reserve’s ecosystem!

photos: Coyote family- Ivan Turpin; Pocket Gopher and Coyote with Pocket Gopher- Duy Nguyen; CA Ground Squirrel- Jane Lazarz; Cottontail- Brian Bradford; Striped Skunk- Ed Smith; Northern Raccoon- Carl Jackson