creatures of the night

Burrowing Owls

Burrowing owl group

Burrowing owls (Athene cunicularia) range from western Canada, through the western United States and southward all the way to the tip of South America at Tierra del Fuego. A separate subspecies is found in Florida and the Caribbean Islands. These owls prefer open land, deserts, prairies and grasslands. They often occur at the edges of disturbed agricultural land, housing developments, and golf courses.

Burrowing owl range mapThe Arizona-Sonora Desert Museum has recently acquired two young burrowing owls which will soon be made available to Docents to handle and interpret.

Burrowing owls are relatively small, with a body length of 7 to 10 inches and a wingspan of about 22 inches. Unlike other raptors where the female is larger than the male, burrowing owl adult males and females are about the same size. They have long legs and short tails.

True to their name, burrowing owls live underground. They may dig their own burrows in soft soil, but more often appropriate holes dug by other animals such as squirrels, prairie dogs, or skunks.

They feed during both the day and night and are most active in early morning and at dusk. They feed on insects, rodents and small reptiles. According to the Cornell Lab of Ornithology, “The Burrowing Owl collects mammal dung and puts it in and around its burrow. The dung attracts dung beetles, which the owl then captures and eats.” It seems they are ranchers.

The female lays five to ten white eggs in the burrow which hatch in about four weeks. The chicks stay in the burrow for about 40 days until they are ready to fledge. For protection, the chicks can make a noise very similar to a rattlesnake. Listen to the various calls from Cornell here. The one that sounds like a rattlesnake is the “Juvenile alarm call” at the bottom of the list. See 5 minute video: https://www.youtube.com/watch?v=3gdU6FHSlXk

Burrowing owls are social and may live in colonies. See more images here.

Related articles:

Barn Owls

Cactus Ferruginous Pygmy Owl – is it a real species?

Great Horned Owl

Western Screech Owl

Creatures of the night – Pocket Mice

Pocket mousePocket mice are well-adapted to desert living. They seldom drink water and can exist entirely on a diet of dry seeds. They are able to live on the small amount of water produced from metabolizing carbohydrates.

According to the Arizona-Sonora Desert Museum (ASDM): “They spend the days underground in the burrow, where in summer the humidity is higher and the temperature lower than above ground. The entrance hole is usually plugged to keep the moisture from escaping to the dry air above. The kidneys of these rodents concentrate the urine to a viscous consistency, reducing water loss. When temperatures become extreme, some pocket mice go into a torpor, or estivate [short-term temporary hibernation]. These animals are solitary and defend small territories, often fighting when they encounter each other.”

Pocket mice are almost entirely nocturnal. During the night, they forage for seeds, eating mainly mesquite beans and the seeds of grass, creosote bushes, and other plants. They carry the seeds in cheek pouches and cache them in their dens.

Pocket mice are in the family Heteromyidae. ASDM says “Despite their names, they are neither rats nor mice; and in spite of their mouse-like appearance, they are not closely related to any other species of North American rodent.” But pocket mice are in the same family as Kangaroo rats which are also able to live on moisture derived from dry seeds. (Is this classification taxonomic nitpicking?)

There are 35 species in North America according to Encyclopedia Britannica , which they describe as follows:

The nine species of silky pocket mice (genus Perognathus) are very small, weighing from 5 to 30 grams (0.2 to 1.1 ounces) and having a body length of 6 to 9 cm (2.4 to 3.5 inches) and hairy tails 5 to 10 cm long. Silky pocket mice have soft fur ranging from yellowish to gray on the upperparts and white to buff on the underparts; soles of the hind feet are furry, but in all other pocket mice the soles are hairless.

The 15 species of coarse-haired pocket mice (genus Chaetodipus) are larger on average, weighing 15 to 47 grams and having a body length of 8 to 13 cm and hairy, tufted tails as long as or much longer than the body (up to 15 cm). Coarse-haired pocket mice are similar in colour to silky pocket mice, but the fur is harsh and the rump has spiny bristles. Silky and coarse-haired pocket mice range from western Canada and the United States into southern Mexico, where they inhabit open desert country.

The five species of spiny pocket mice (genus Liomys) are found in extreme southern Texas, but they live mostly in Mexico southward to Panama in semiarid brushy and rocky habitats. These pocket mice weigh 34 to 50 grams and have a body length of 10 to 14 cm and long tails of up to 16 cm.

The seven species of forest spiny pocket mice (genus Heteromys) are the largest, weighing from 37 to 85 grams and having 11- to 18-cm bodies and long scantily haired tails. Forest pocket mice range from southern Mexico to northern South America, where they live from sea level upward into mountains. All the spiny pocket mice have harsh fur made up of stiff, bristly hairs that may be gray, reddish brown, dark brown, or glossy black. In some species a rust-coloured strip separates upperparts and underparts

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See photos from Google Images. You will notice quite a variation in color. Apparently pocket mice can evolve rapidly to take on the color of their surroundings. There have been several studies of this feature, for instance:

The genetic basis of adaptive melanism in pocket mice: “Rock pocket mice are generally light-colored and live on light-colored rocks. However, populations of dark (melanic) mice are found on dark lava, and this concealing coloration provides protection from avian and mammalian predators.”

ASDM notes: “Because there are many of these little rodents and they are closely related to each other, each species has evolved with different foraging times and places, which minimizes competition. Bailey’s pocket mouse, for example, climbs up into desert wash vegetation to find seeds and berries still on the plants, while the desert pocket mouse hunts along the ground in washes and open areas for seeds. Merriam’s kangaroo rat, a creature of open, creosote flats, tends to dash from one clump of bushes to the next, overlooking seeds out in the open spaces, leaving those for other mice to find. In this way many species of heteromyid mice and rats can share the same environment.”

The website: http://www.nhptv.org/wild/heteromyidae.asp lists 62 species of the family Heteromyidae world-wide (this includes kangaroo rats).

Related articles:

Creatures of the Night: The Bats

Creatures of the Night: Kangaroo Rat

Creatures of the Night: Grasshopper Mouse

Creatures of the night – Ringtails

Creatures of the Night – Skunks in Arizona

Creatures of the Night: Bats

Big-brown-bat-Paul-BerquistBats have been around for at least 50 million years and in that time have evolved to take advantage of a great variety of habitats. The more than 1,000 species live on all continents except Antarctica and occur everywhere except in polar regions and in extreme deserts. They range from the very tiny, weighing less than a penny, to giants with wingspans over 6 feet.

Bats come in many colors: black, white, yellow, brown, orange, red, and blue-gray. Bats are mammals and have adapted almost every mammalian feeding strategy. Some are carnivores and hunt small rodents, birds, lizards, and frogs. Some are even fishermen. Some bats are herbivores and feed on plant nectar and fruit. Other bats are insectivores and play a large part in keeping insect numbers in check. And some bats are parasites; these are the vampires that survive by feeding on blood from other animals.  (The vampire bats don’t suck blood, they make a small incision and lap  up the blood.)

Lesser-Long-NoseBats are important pollinators for a variety of plants including the saguaro and other cacti. The fruit eaters help disperse the seeds.

Bats can fly, maneuver, and locate insects in complete darkness due to their acute hearing and practice of echolocation. Bats emit a sound, mostly in frequencies higher than human ears can detect. That sound bounces off objects and prey, and returns to the bat. The bats judge distant by the time delay of the returning sound.

Bats are not blind. Bat’s eyes contain rod photo-receptors for night vision and cone photo-receptors for daylight and color vision. They can see into the ultraviolet which helps them maneuver in twilight and better recognize UV-reflecting flowers during the day.

Bats live in crevices and caves, mines, under bridges, in attics or barns. Some bats hibernate, others migrate. I have a family of bats living somewhere near my house. At dusk on summer evenings, they come out and drink, on the fly, from my pool.

Bats, like other mammals, can carry rabies which is fatal to humans. The virus is transmitted by a bite. According to the CDC, it can also be transmitted when the saliva from a rabid animal comes in contact with a person’s mouth, eyes, nose, or a fresh wound. Some studies indicate that about 5% of the bat population carry rabies. Histoplasmosis, a fungus associated with bird and bat droppings, can become airborne and inhaled. Most infections are mild and produce either no symptoms or a minor influenza-like illness. On occasion, the disease can cause high fever, blood abnormalities, pneumonia and even death. The CDC says that “research suggests that bats might be the source of several hemorrhagic fevers, which affect multiple organ systems in the body and often lead to life-threatening diseases.” They also found bats carrying the deadly Marburg virus. Bats suspected of carrying these diseases live in Africa.

Bats, themselves, are subject to disease. Recently “white nose syndrome” has killed millions of bats mainly in the northeast U.S. This disease is suspected to be a fungus.

There are many places to observe bats around Tucson such as Saturday summer nights at the Arizona-Sonora Desert Museum. Other good places around Tucson include the East Broadway bridge over the Pantano Wash, the North Campbell Avenue bridge over the Rillito, and the East Tanque Verde bridge over the Rillito.

You can find photos and fact sheets on several bats of the Sonoran Desert here.

At Bat Conservation International you can find information on building bat houses and on how to safely and humanely remove a bat from your house.

Creatures of the Night: Grasshopper Mouse

Mice will eat just about anything, but most prefer plant parts. The grasshopper mouse, however, is a ferocious carnivore. It eats grasshoppers, beetles, spiders, centipedes, millipedes, worms, lizards, scorpions, snakes, and other mice. It hunts like a cat and defends its territory by howling – it is the mouse that roars.

GrasshopperMouse1 (1)

There are several species and most inhabit the grasslands of the great plains, but at least one species is a desert dweller. The Northern Grasshopper mouse has a range from Canada to Mexico, and California to Minnesota; the Southern Grasshopper mouse has a range that includes parts of Nevada, Arizona, New Mexico, and Texas. The southern species is gray-brown- to cinnamon colored with a short white-stripped tail. Most grasshopper mice are relatively stout compared to other mice. The head and body is 3.5″- to 5″ and the tail is 1″ to 2.5″ long.

Usually a male-female pair live together and defend a territory. It marks the territory with musk.

Grasshopper mice have very strong jaw musculature required for killing prey. And they learn quickly how to deal with various prey. One observer describes how the mouse dealt with a 3-inch scorpion in Arizona: ” The mouse would first nip the tail so that the stinger was ineffective. It would then stand the scorpion on end, holding it with its front paws, and methodically eat the writhing creature head first.”

The grasshopper mouse is a nocturnal hunter, a good climber, and active year round. In some areas, scorpions account for almost their entire diet, which might be surprising because the mice are not known to have any immunity to scorpion venom.

GrasshopperMouse2

These mice will eat seeds, grasses, and grains, and cache them, like other mice, but about 90% of their diet is animal matter. The strangest part of their diet is sand. Biologists think the mice eat sand to aid in digestion, just like some birds ingest gravel. And that’s not all that is strange about their digestive system. As described in an article by Mary Ingle: “A pouch attached to the underside of the stomach opens into it via an aperture too small for large food particles to pass through. The pouch contains all of the gastric glands that contribute to the breakdown of food and are normally found in the stomach of other mammals.” Ingle speculates that the pouch exists because the insect diet would be too rough and damaging for delicate gastric glands to function normally.

The grasshopper mouse digs four kinds of burrows: nesting, retreat/sleeping, caching, and the bathroom.

The mice have several vocalizations. You may have heard their territorial proclamation and mistaken the high-frequency sound for that of an insect. So now, when you are out at night, listen for the mouse that roars.

For a video of a battle between a grasshopper mouse and a very large centipede check here: http://tinyurl.com/ylyme9w Note that centipedes are venomous.