NATURAL HISTORY OF ENSATINA
The most frequented habitats for Ensatina are near streams in an oak woodland or coniferous forest. During wet weather they may be found under bark, logs or even rocks. They tend to be found on gently sloping or level ground, or less frequently on steeper slopes. Ensatina seem to favor ecotones that are the edge of dense woodlands adjacent to clearings, meadows or grasslands. There are fewer numbers in dense forests such as those very wet redwood forests of North West California. Populations of Ensatina tend to inhabit denser forested areas in high mountainous area (croceater and klauberi) or are troglodytic (eschscholtzi) at lower, more arid oak forested foothills. Populations of Ensatina are less dense in chaparral or grasslands, or in areas without a source of free water. In very dry regions of Southern California, Ensatina often inhabit narrow areas located adjacent to springs or small streams.
During the cold winter or dry summer months, they will retreat down into mammal burrows, interior of rotten logs or down rotten tree roots.
Ensatina can be found at elevations ranging from sea level up to 10,000 feet in the San Bernardino Mountains.
All subspecies of Ensatina are strictly nocturnal when it comes to being active on the ground surface. In addition, they most are active on the ground surface during rains that come during the night. Although it may be raining all day, if it clears and rain has completely stopped at night, very few individuals are active on the surface. If air temperatures fall below 40°F, very few active individuals can be observed.
Activity of Ensatina occurs during fall before snows come and during spring after snow has melted. Often they can be found under logs or bark if snow cover is less than 50%. If there is a light snow storm during late spring months, Ensatina can be found under logs showing recent activity. In the middle of winter months, for example January, Ensatina may be active at night if the rains are relatively warm (40°F and above).
All Ensatina found in the first fall rains seem to be well nourished. That probably means that they are actively feeding under ground in mammal burrows during the summer months, or that that they have low matabolic rates due to low temperatures and minimal activity.
DIET AND FEEDING BEHAVIOR
The diet of Ensatina includes many small insects (crickets, earwigs, ants, termites, beetles), spiders, small scorpions, centipedes, millipedes, sow bugs, pseudo scorpions, snails, and worms. They are equipped with a relatively long, sticky tongue with which they can grab small arthropods or worms. ( see feeding behavior ).
Ensatina have tails with a high density of poison glands. When first picked up by a person, they sometimes move vigorously and secrete a white sticky poisonous fluid from their tails. If a person gets this poison on their lips, a part will become numb that lasts for several hours. It is not known how poisonous the tail would be to a human if consumed. When Ensatina is attacked or irritated, they may assume a defensive posture by standing high while arching its back and secreting a whitish sticky toxic fluid from its tail that is arched high above the ground surface. During this pose, the tail is waved from side to side.
Among the predators of Ensatina are the raccoons. Adult raccoons will eat Ensatina beginning with the head down to where the tail begins, and the tail is then discarded. Young inexperienced raccoons will mouth over an Ensatina, but instead of eating it, the young raccoon will spit it out.
Other predators include owls, bears, snakes, jays, other salamanders, frogs, and shrews. Because of this predation, Ensatina have evolved protective coloration that mimics either the background color caused by leaf molds or the color of the highly poisonous newts. It has been proposed that the relatively bright orange coloration of xanthoptica is mimicry of newt coloration. (Kuchta, S.R., 1998; Stebbins, R.C., 2003)
DENSITY AND DISPERSAL
One estimate of Ensatina density for adults (Contra Costa County) was 170 – 200 per acre. Densities for Ensatina populations will, like all species, vary according to a number of factors such as resource availability, climate, and topography.
Generally, Ensatina has a low dispersal distance. In one study (Staub, N. et al, 1995) at Calaveras Big Trees in the Sierra Nevada, it was found that the maximum distance any male moved was 120.4 meters, whereas for females the maximum distance was 60.5 meters. This is a relatively small distance when one considers the entire state of California. Thus the dispersal rate or the spreading rate for Ensatina may be as little as 100 meters a year in favorable habitats. Dispersal may be accelerated if Ensatina individuals are washed downstream during floods. They are poor swimmers. Most will not voluntarily go into a stream or lake, but if washed into a stream by flooding, they can be transported downstream for quite some distance. One example of a river that may have accelerated platensis north to south dispersal is the long Kern River that flows from Sequoia National Park south all the way to Bakersfield, over 100 miles long.
Salamanders have a highly vascularized moist skin. It is across the epidermis that gas exchange occurs and oxygen is transported to all parts of the body. Frogs and some salamanders have lungs that also act as a gas exchange surface. Larval forms of salamanders that breed in the water have gills. However, Ensatina has neither lungs or gills. Oxygen is taken into their bodies mostly via the epidermis. Only a small percentage is obtained through the inner surfaces of the mouth interior; the buccopharyngeal region. Using a dissecting microscope, one can see the blood surging through capillaries that permeate the entire body surface. It is essential for the gas exchange and thus the survival of Ensatina that the entire body is kept moist.
COURTSHIP AND MATING
Male Ensatina have longer tails than females. The bodies of females are usually stouter and shorter than the slim bodies of males. In addition males have a protruding upper lip. A nasolabial groove extends downward into this upper lip in both males and females. Studies have shown that Ensatina will “stub” its upper lip while moving across ground surfaces. The nasolabial groove will pick up water from the ground surface. The water then moves up the groove via capillary action into the nasal chambers. Ciliary action moves this liquid across olfactory receptors and by this means a salamander can detect various types of chemicals found in the water. (Brown, C.W., 1968)
During rains and at night, males and females are moving about on the surface of the forest floor. There is little light and many obstacles on a forest floor such as logs, rocks and vegetation. Males and females can locate one another by olfaction, using the chemicals picked up from the forest floor, in particular secretions from their bodies.
Stebbins observed courtship in Ensatina. He describes the courtship as follows: when a male is close enough to see the female, he first creeps up to the side of the female. He moves up to her head, then noses the side of her neck and head. He then slides his body past her moving beneath and against her gular area until his sacral area is against her throat. What follows is a “tail walk” during which the gular region of he head is resting on the pelvic region of his body. At times he will move his pelvis back and forth while she moves her head back and forth thereby rubbing her gular region on his pelvic area. He will eventually stop and deposit a spermatophore (sperm capsule) on the ground. The sexual act is consummated when the female squats on the spermatophore, taking it into her cloaca by means of the lips of her vent. At the same time the male lurches backwards, frees his long tail, and throws it over her back. The distal part of the tail is writhed violently and is moved in a stroking fashion over the back and tail base of the female. The two then separate, but in a few minutes they may court again. A female may mate with the same or other males later. Sperm will move from the capsule into a storage chamber of the female that is called the spermatheca. It is thought that sperm may last as long as a year in the spermatheca. (Stebbins, R.C., 1949; Stebbins, 1954)
OVIPOSITION, HATCHING, AND GROWTH
Eggs are usually laid during the months of April and May in a quiet moist location under bark, rotten logs or most likely under ground in mammal burrows. Females may lay from 3 to over 20 at any one time. Eggs are probably fertilized at time of laying. From the time of egg laying in April to hatching in August or September, the female broods her eggs. During brooding, the female often rubs her gular region on the eggs, and that apparently protects the eggs from lethal fungal infections. Some 95% of the eggs will develop fungal infection and die if the female is removed.
(after Stebbins, 1954)
Newly hatched young are only about 30 millimeters long. Growth of the young requires three to four years before sexual maturity, when they have reached about 80 millimeters in length. They seem to live less than 10 years in nature. However they have been kept in captivity for 8 years after they were captured as a full grown adult. For that reason, Ensatina may live up to and possibly older than 20 years in ideal captive conditions.
ENSATINA IN CAPTIVITY
Ensatina are very sensitive to ambient conditions. Most people should not attempt to keep them as pets because the captive environment must provide a gradient of temperatures and moistures to minimize stressful conditions. In captivity in such ideal conditions, they are seldom seen; therefore it is not practical to keep them as “pets.” Special wood cages of fairly large sizes that are equipped with layers of thin boards and an automatic watering system are required. Most of the time, Ensatina should be able to move from the wettest part of the cage to a dryer part as well as moving from a cooler parts to a warmer spot as needed. A small 20 or 40 gallon aquarium is simply inadequate to properly keep Ensatina alive and healthy in captivity. Those kinds of captive conditions are always stressful.