Mammals of Blue Sky

by Alan Torretto

In the spring of 2017, I was leading one of my biology classes on a hike in Blue Sky. As we walked along the Creekside Trail, one of my students spotted a dead deer. As I peered through the vegetation I noticed it was a female mule deer. Her thoracic and abdominal cavities were torn open, and the heart and liver were missing. It was a fresh kill. Because of the noise that we were making, had we scared off the mountain lion(Puma concolor)? I am sure the lion was hiding nearby waiting for us to leave. When I returned to the spot after school ended, the carcass was gone. The lion had dragged it off to a more remote area to feed on it.

This is an example of an interaction between two of the many species of mammals that Blue Sky’s habitats support. These big cats probably don’t live in Blue Sky, but it is definitely part of their hunting grounds. A research survey of North America found that 68% of their prey items were ungulates, especially deer. Mountain lions are typically ambush predators, taking one deer about every two weeks.

Indigenous to western North America, the mule deer (Odcoileus hemionus)is named for its ears, which are large like those of the mule. Studies show that some 788 species of plants are eaten by mule deer, depending on the season, geographic region, and elevation. In Blue Sky, acorns are one of its favorite foods. Average lifespan for mule deer is a robust 22 years, making them one of the longest living deer species.

Mule deer carcass Mountain Lion Mule Deer

Kangaroo rats (Dipodomys merriami) are named for their extremely long, kangaroo-like hind feet and they are almost completely bipedal. They hop or jump rather than scurry or run. Their relatively long tail acts to counterbalance the hopping/jumping form of locomotion. Most kangaroo rats are exclusively nocturnal. During the day, they remain in their cool burrows. The diet of Merriam's kangaroo rat is almost exclusively plant seeds. They rarely drink water. Rather, they obtain water through metabolic processes augmented by the moisture content of their food.

Desert cottontails (Sylvilagus audubonii) are herbivores, with 90% of their diet consisting of grass. They also feed on the leaves of other plants and the juicy pads of Prickly Pear. Cottontails rarely need to drink, getting most of their water from the plants they eat or from dew. The lifespan of a cottontail that reaches adulthood averages less than two years. Mated pairs of Cottontails have multiple litters throughout the year. They are preyed upon by many of Blue Sky’s carnivores.

California ground squirrels (Otospermophilus beechey) are the most observed of all Blue Sky’s mammals. They live in burrows, which they excavate themselves. Some burrows are occupied communally, but each squirrel has its own entrance.These little guys use their cheek pouches to store more food than can be consumed in one sitting for a later time. They are mostly herbivorous, with seeds, grains, nuts, fruits, and sometimes roots, constituting most of their diet. Female ground squirrel have one litter of between five and eleven young per year, with gestation around one month.

Merriam’s Kangaroo Rat Desert Cottontail. California Ground Squirrel

Coyotes (Canis latrans) are often spotted alone or in packs of up to four individuals. Primarily carnivorous, their diet consists mainly of deer, rabbits, rodents, birds and reptiles. They will also eat fruit like manzanita berries and mesquite pods. They usually breed between January and March and produce 1 litter per year. The average litter size ranges from 4 to 7 pups. The sound of coyotes howling is one of my favorite sounds of the wild.

In my opinion, one of the “cutest” and one of the rarest mammals in Blue Sky is this little masked carnivore. Don’t let its “cuteness” fool you - it is a deadly hunter! The long-tailed weasel (Neogale frenata) is a fearless and aggressive predator attacking animals far larger than itself. Rodents are its main prey, but shrews, moles, rabbits and birds are also taken.

Raccoons (Procyon lotor) from the procyonid genus which includes ringtails, kinkajous and coatis. These small mammalian carnivores have powerful jaws and teeth. They have highly-developed nerves in the pads of their front paws that function almost like a second set of eyes, helping them identify objects and food sources. Since they are typically nocturnal, raccoons rely on touch and scent more than they do on sight.

Gray foxes (Urocyon cinereoargenteus) have been spotted more frequently in Blue Sky in the last couple of years. They eat a wide varieity of foods including mice, rabbits, squirrels, birds, insects, fruit and even carrion. They typically live 6-8 years in the wild. Gray foxes have oval pupils, unlike the red fox which has slit-like pupils. Its strong, hooked claws allow it to scramble quickly up trees to escape predators like coyotes.

Coyote Long-tailed weasel Raccoon Gray Fox

DECOMPOSERS: BREAKING IT ALL DOWN

by Alan Torretto

Sixty years ago when I was in 4th grade, my teacher explained to the class how Squanto (a Native American) taught the Pilgrims how to plant corn. He told them to always place some dead fish in the ground with the corn seeds. He knew that the dead decomposing body of the fish would help the corn grow healthy and strong. Although that was 405 years ago, Squanto understood the importance of the process of decomposition.

Decomposition is the process of breaking down complex chemical compounds in dead plants and animals into simpler chemicals containing nitrogen, phosphorous, potassium, calcium, etc. that plants can take up. It is important because it recycles these chemicals and makes them available for new or growing organisms to utilize.

Nature’s unsung recycling heroes - organisms that “feed” on the remains of dead organisms

The primary decomposers of most dead plant material are fungi. These include mushrooms, molds, and slime molds. They produce powerful enzymes that break down complex carbohydrates and proteins found in dead plant cells.

From left to right: Orange Bonnet, Chocolate Tube Slime Mold, Hedgehog Scalycap, Bear Lentinus, Oyster Mushroom

Mushroom

The “mushroom” is only the reproductive structure of the fungus. The “tube like” mycelium produces the enzymes that break down the host plants tissues.

Not all fungi are decomposers, many are parasites.

decomposition of animals

From dead rabbit to rabbit bones

Five general stages of decomposition in animals are:

1. Fresh

2. Bloat

3. Active decay

4. Advanced decay

5. Dry/remains

When an animal dies, bacteria inside and outside of its body begin to break down tissue. Smell coming from this process attracts flesh flies and vultures. The flies lay eggs, which become maggots that further eat the tissue. Vultures tear off large chunks which allows more bacteria to enter and accelerating the process. The final step is carrion and burying beetles removing the last tissues from the bones.

Endangered and Threatened Species of Blue Sky

Text and most pictures courtesy of Al Torretto.

Among the many reasons natural areas like Blue Sky Ecological Reserve are set aside and protected is to preserve essential habitat for Endangered and Threatened species. Blue Sky has several endangered and threatened species.

What is the difference between an endangered and threatened species? An endangered species is facing a very high risk of extinction in the wild. A threatened (or vulnerable) species is facing a high risk of extinction in the wild.

Orange-throated Whiptail (Aspidoscelis hyperythrus): This species of lizard is native to Southern California. Because of its limited range, it is endangered by habitat loss due to urban development. Blue Sky and Cabrillo National Monument in Point Loma are some of the few areas in San Diego County where they can be found.

Coastal California Gnatcatcher (Polioptila californica ssp. californica): The Coastal California Gnatcatcher is a small, threatened non-migratory songbird. It has black, gray, and white feathers, and eats mainly insects. It often lives alone but joins with other birds in winter groups. Preserving its Coastal Sage Scrub habitat is essential for its survival and played an important role in acquiring some of Blue Sky’s acreage.

Red Diamond Rattlesnake (Crotalus ruber): This beautiful snake is a venomous pit viper found in southwestern California and Baja California. NatureServe rates it as Vulnerable which means it’s considered at moderate risk of extirpation due to a fairly restricted range, relatively few populations, and recent and widespread declines.

Least Bell’s Vireo (Vireo bellii ssp. pusillus): Bell’s Vireos are found along streams or in dry arroyos. Even when large trees, like cottonwoods and willows, are present, they tend to stay in low vegetation. They feed primarily on insects (especially caterpillars) and spiders. The Least Bell’s Vireo is on California’s List of Endangered Species due to a significant range-wide decline related to extensive habitat loss due to urban development, exotic plant invasion, and expansion of agricultural practices into riparian zones. Brood parasitism by the Brown-headed Cowbird has also been identified as an issue.

Bald Eagle (Haliaeetus leucocephalus): I have studied wildlife in Blue Sky for over 45 years, and had never seen our national bird here. That changed this spring when I saw my first one flying overhead as I walked down the main trail. Bald eagles have been spotted at Lake Poway for several years. They use both Lake Poway and Lake Ramona as fishing grounds.

San Diego Sagewort (Artemesia palmeri): Threatened. This rare species of sagebrush is native to only San Diego and Northern Baja. Most of its habitat has been destroyed by human land development. Blue Sky is one of the few areas that has a “healthy” population of this species. It can be found along the Green Valley Truck trail and the Creekside trail.

Delicate Clarkia (Clarkia delicata): Vulnerable. This beautiful and delicate little flower grows in the oak woodland and chaparral habits in Blue Sky. It is only found in San Diego County and Northern Baja. Look for it in the spring growing along the main trail in April, May and June.

Quino Checkerspot Butterfly San Diego Fairy Shrimp Hermes Copper Butterfly

Although these endangered species have yet to be discovered in Blue Sky, the Reserve does have the habitat requirements that they need, and they have been found a few miles from Blue Sky’s location.