The Cotton Rat: Pest or Prey

I sit all day in a bird blind, on a private ranch, in southern Texas. It is April and the neo-tropical bird migration is in full swing. It cost a tidy sum for the privilege of sitting here, and I hope to get my money’s worth. Not only birds visit the feeding area in front of me, but a few mammals. One mammal that is a frequent visitor is a Cotton Rat. I discuss the occurrence of the rats with my host, who educates me to its relationship with the area’s Bobcats.

The Cotton Rat is named for its habit of building its nests out of cotton. This can be a major problem for cotton farmers. This rodent is found in southern Arizona, southern New Mexico, southern Texas, and into Mexico. It likes tall grass areas or cultivated fields. Like most rodents, it is very prolific – having 5 litters a year of 7 to 10 young at each nesting. The young leave the nest at 2 weeks of age and start breeding at 6 weeks. Wow! What a reproductive machine!

They are omnivores: eating grass, sedges, domestic grains, insects, and eggs. This 9 to 11 inch (1/2 pound) rat can be a real concern for agriculturists. Populations erupt over several years, but then crash – disease being the major cause. Coyotes, and especially Bobcats, find them as a major food source where the rat occurs. Bobcat populations of those southern areas rise and fall in direct relation to the rat’s population cycling.

Besides serving as prey, there is another benefit derived from this very pugnacious and quarrelsome rodent. They have proven to be useful in influenza virus research.

Sigmodon fulviventer in a feasting mode

A Gift from Nature

Sea Otters, like all otters, are delightful creatures. We usually see them in a group off shore, out of range – oft-times entwined in beds of kelp. Seaweed keeps them from floating off. I’ve yearned to get close to them, without much success. It was a major surprise; when, after several aborted attempts, that we came upon a single. He was far from any group and was only ten feet from shore. He was definitely where he didn’t belong. He had perfect trust in us. It was a gift from nature. It couldn’t be anything else.

Sea Otters are brown and the older males have white faces. Males are also slightly larger than females. They have short tails and webbed feet – the back ones are flipper-like. Our Southern Sea Otter is found from Alaska to California, where they inhabit the coastlines within a mile of shore.

They spend their life at sea – eating, sleeping, mating, and even giving birth in the water. A new pup, two are rarely born, will ride on mom’s chest and will nurse up to a year before weaning. The female will make a cooing sound while she is nursing, and the babies will cry if they get separated from the group.

Most of their non-scavenging time is spent floating on their back, where they eat sea urchins, crabs, mussels, fish, and their favorite food – Abalone. A rock makes a handy tool to smash shells open to get at the meat. The prey is laid on their chest and then pounded with the rock. A 55 pound otter requires 13 pounds of food a day. That’s 1/4th of its body weight.

Sea Otters can stand in water to scan for danger, which they do by shading their eyes with a paw, Alarmed, Mom will grab Junior and tuck him under one flipper and dive. They can remain submerged up to four to five minutes. Otter fur is the thickest in the mammal world. It keeps them warm and buoyant. When not eating or sleeping, they are always preening – looking as if they are constantly scrubbing face and body and then rolling over as if to rinse off.

Sea Otter floating on his back

Coming upon this individual was indeed fortunate and I’m thankful for this gift from nature

The Red Fox: Observations of Learned vs Innate Behaviors

The Red Fox has so many and varied behaviors that it makes for an interesting study subject. It is also interesting to try to determine where innate actions end and learned ones take over.

Certainly what is eaten, and the urge to store the left-overs for later consumption, has to be an innate response. Likewise, the rising up on the hind legs to pounce on prey, as well as the urge to mark territory through urination – would, I think, be programmed at birth. Like all animals, their DNA code and resulting actions are inescapable.

But the fox demonstrates much that has to be learned and indicates a keen intelligence. The complex variety of vocalizations and certain hunting techniques would have to be copied from their parents. When parents bring back live rodents for the young to practice with, shows that school is definitely in session. Parents will also hold prey in their mouths, while moving their heads from side to side and up and down. This forces the pups to exercise and gain agility in their hunting movements.

A very good example of this animal’s intelligence is how they have learned to avoid the fox hunting chase by doubling back and running down the middle of a stream to erase their odor trail. Another intriguing behavior is called “charming”. Instead of dashing into a group of rabbits, who would then quickly escape, the fox will roll on the ground and chase its tail in a seemingly unconcerned attitude. The rabbits will curiously watch, but the predator slowly rolls close enough to suddenly spring and catch a rabbit.Is this behavior learned or innate? Your guess is as good as mine.

One fact, however, is that the more learning that is required – the more important play becomes amongst the young. Play also establishes dominance rankings and that reduces future adult conflicts.

A young fox checks me out

A young fox checks me out

Estivation and Lizards

Estivation is a condition of dormancy or torpor during very hot or dry seasons. It’s like summer hibernation. Snails, salamanders, frogs, desert tortoises, snakes, and lizards are some animals that estivate. The only known mammal to do so is the Malagasy Fat-Tailed Dwarf Lemur. The snakes, which I kept in my High School classroom, were forced to estivate during the summer when no one was around to feed them.

The most abundant reptiles are lizards (about 3000 species world wide) – most of which live in hot areas. They are some of the more common species that Estivate during the hot times. Lizards usually have four legs, with five toes on each foot. Their skin is dry and scaly, eyelids are moveable, and ears are on the sides of their head. If you’ve ever tried to catch one, you know how fast they can move. I’ve caught them by using a fishing pole with a loop on the end of the line. By reaching the pole as far as I could, I’d carefully drop the noose around their neck and then pull it tight.

Most lizards are carnivorous but some, like iguanas, are vegetarian. For reproduction, the female lays her eggs, covers them, and then lets the warmth of the sun hatch the young – six or seven is the most common number. However, some species give live birth.

Because their body temperature is the same as the air around them (cold blooded), a burrow is extremely important to escape cold or the extreme summer heat of the desert which would cook them. The burrow is also an escape from a predator that ventures too near. Otherwise, they will remain motionless and rely on their camouflage to escape the danger.

Lizards send visual signals by head or body “bobbing” – each species has its own signature method.

A dark phase Western Fence Lizard at attention on a rock

A dark phase Western Fence Lizard at attention on a rock

Elk: Majestic Forest Denizens

Cervus elaphus, or Wapiti are large and very striking beasts. To hear their bugling on the autumn air is moving and unforgettable. A group of them on a hillside lends a definite aesthetic quality to the surroundings. They are wide spread over the west in high, open mountain meadows. Winter sees them more often in the trees, seeking thermal cover.

Elk can run 35 mph and are strong swimmers. They are, also, very hardy and can withstand the harshness of winter better than deer. When the food supply is short, they will strip the bark from trees. Thus, they can destroy their own habitat – a recent problem in Yellowstone Park. Mountain Lions and Wolves are their major predators. Predators are a benefit to them by keeping their productive population numbers in balance with the food supply. Cattle that get too thin will fail to reproduce, or to even come into estrus. Elk are no different. Food supplies definitely affect reproductive success.

Old velvet itches and the bulls will thrash it off on bushes. This action stimulates the production of testosterone in preparation for the rutting season. Fights for dominance then occur but injuries from them are rare, except on occasion when antlers get inter-locked resulting in death to both bulls. Besides bugling, bulls will urinate on bushes, wallow in murky water, mud, and urine. I don’t know whether this attracts the cows or releases some of the male’s stress. Harems are collected, of up to 60 cows, which the dominant bull will herd to keep assembled. There is a price to pay for this privilege – loss of important fat needed to survive the upcoming winter – and many of these bulls will not live until spring. The resulting calves are born in spring and feed only on milk for their first month and are weaned at nine months.

This animal, a favorite of many hunters, is adaptable enough that species numbers are greater now than when Europeans first settled in this country. Some years ago, when we first entered Yellowstone at the north entrance portal, a huge bull, with gigantic antlers, was posing on the hillside as if to welcome everyone into the park.

An elk bull in autumn prime

A bull in autumn prime

Sign Stimuli

Just looking at another animal does not stimulate a response. That which does stimulate is the result of signals. Signals can be changes in color, special body movements, special aromas, special sounds, and different positions of body parts. Tail position, or movement, is important to canines and Bison. Ear position is important to bears. Special smells and sounds are vital in courtship behavior, and movement can either be stimulating, submitting, or threatening. This is why a person must walk quietly, and not make any abrupt movements, when moving among either wild or domestic beasts – so as to not stir them up.

Colors are signals to lizards, fish, and birds. If an animal is colored, it can see color – not color blind like many mammals (who depend on light and dark shades). Many bird species utilize color, and because they are built differently than quadrupeds, crest feathers become important signal senders. Even if a species has no crest, the raising of feathers or wings become strong stimuli. Cardinals, Jays, Pyrrhuloxia, Phainopepla, and Titmice are some very notable birds with crest feathers.

The small Black-Crested Titmouse’s crest is certainly eye-catching and important in mate selection. Crests that are raised higher than usual, or forward, can indicate an aggressive mood – likewise the lowering of them can mean the opposite. Another sign stimuli of this bird is its alarm call. The alarm is a loud scold that fades away. Predators think that the prey has fled the scene and has given up the chase. The bird, however, is still nearby but hidden in a bush.

This songbird measures 5 ½ to 6 inches at maturity. It loves to live wherever there is rampant tree growth, as they nest in tree cavities. In areas of urbanization, the Black-Crested Titmouse will also nest in telephone poles, fence posts, or man-made birdhouses. Urban shade trees, heavy timber, and deciduous forests may all be home to the Black-Crested Titmouse. It enjoys feeding on nuts, seeds, berries, spiders, insects and insect eggs.

A Black-Crested Titmouse - Very alert, on a lichen covered branch

A Black-Crested Titmouse – Very alert, on a lichen covered branch

Black Bears and Individual Distance

INDIVIDUAL DISTANCE is a moving space around an individual’s body that others are not allowed to enter unless either mating or fighting. Different species have specific requirements, as well as, individuals within each species. Bears are no different. They are real attractions but are dangerous to approach, and it’s best not to approach them. However, their ears give off visual signals. Erect ears usually go with an alert look which indicates the bear is curious and checking you out. It’s when they lay their ears back that they are indicating that their space is being violated.

Black Bears are solitary beasts and so they naturally have great space requirements. They work to maintain a distance from other bears and perceived enemies. A male bear uses up to a 200 square mile area, while a female requires 35. They use the same trails year after year and have convenient escape routes to maintain their space. Trees are also very critical as a means to escape confrontations.

Black Bears are crepuscular (morning and twilight active), which results in fewer confrontations with Grizzlies. They usually spend most of the daytime and nighttime in burrows. Much of their behavior, although not totally understood by man, is directed to maintaining a distance from other bears. When standing on their hind legs, they are gaining information through better vision and smell. Smell is their best sense. It is said: “That if all smells were as strong to humans as skunk smell, you’d know how great a bear’s olfactory ability is.”

A “woof” is a sign that they have been startled. I experienced that “woof” when hiking up to an Osprey nest in British Columbia. I noticed a blackness in the vegetation by the trail ahead. That was stimulus enough for me to back up slowly the way I had come. If a bear does charge or run, they are extremely fast. They can cover 50 yards in 3 seconds.

Black Bear

A Black Bear, with her ears back, warns me not to come any closer

The Opossum: American Marsupial

Night sounds can be mysterious. One of the intriguing factors of spending a night in the wild, is the crunching, gnawing, growling sounds that inundate your ears. Many of these sounds (hopefully you’re lucky enough to spot the maker) are from creatures that are seldom seen. The Opossum is one of these creatures.

Marsupials in America are indeed seldom seen. As a group, they are very fascinating animals. All Marsupials have pouches, and mammary glands are within the pouch. The American Opossum has thirteen, while kangaroos have only two. The two kangaroo glands produce separate types of milk – regular in one and colostrum in the other. Kangaroos are always pregnant. When one Joey is weaned, the dormant embryo starts to develop and the mammary glands then switch roles in the production of milk. The Opossum however, gives birth to a big litter – more than she can feed. The weaker young, deprived of food, die. It’s a different type of “survival of the Fittest.” Upon leaving the pouch, the babies “hitch a ride” on Mom’s back. She positions her tail pointing forward toward her head. The young cling to the tail like a standing commuter that grasps the overhead railing on a bus.

There are five finger-like toes on both front and back feet and the animal leaves a distinctive circular track. The movement of its feet is called pacing, which is the moving of the legs on the same side at the same time. Other pacers are bears, raccoons, skunks, badgers, beavers, porcupines, and woodchucks. The Opossum is well known for its habit of playing dead when threatened. It has also been a food item (possum) for the poor folk of the southeastern USA. It is a short-lived creature – living about two years in the wild or four in captivity.

In Tennessee, high upon the banks of the Mississippi River is a campground. While camping there, we heard gnawing sounds in the night. It was an Opossum. A very shy animal that would scurry away at the slightest disturbance, but its visceral needs constantly drew it back to where we were camped. This was our first experience with this novel animal.

Our midnight visitor

Goss’s Rule and the Canines of Yellowstone

GOSS’S RULE states: “When two species share the same habitat, and also share the same niche, the dominant species will push its competition out.” This is classic between coyote, fox, and wolf. Yellowstone Park provides a situation where this rule is very noticeable. Before the introduction of wolves, there were many coyotes and fewer fox. Since their introduction, wolves have expanded greatly, coyote numbers have decreased, and the Red Fox population has increased.

It stands to reason that size plays a big role in the dominance of these three canines. Wolves, especially when hunting in family packs (usually 4 to 7), can bring down larger prey than coyotes – hunting alone or even cooperatively. Also, bigger groups contribute to a species ability to dominate, and larger canine will kill the smaller ones when they catch them. I have witnessed wolves chasing coyotes that were brazen enough to approach a carcass fed upon by wolves. I have seen coyotes escape, but also observed one that was unlucky. Because the Red Fox feeds mainly on smaller mammals and birds, it is not as competitive to the wolf as is the coyote – which has an expanded diet.

Gray wolves look like large German Shepard dogs. Coyotes are somewhat smaller, lighter in coloration, and have a more pointed face. The Red Fox is considerably smaller, with a slender body, reddish tinge to its fur, and with a white tail tip.

Vegetation eaters, when their populations increase, have the ability to destroy their own habitat. Thus, predators keep these populations in balance. Predators are also breeding selection factors for prey species. They weed out the weak, the diseased, and the old (who no longer reproduce but still eat). Nature’s ways sound cruel, but they are necessary to keep herbivore numbers at the maximum that the habitat can withstand

A Gray Wolf: Top dog in the predator hierarchy

A Gray Wolf: Top dog in the predator hierarchy

Burrowing Owls: Small, Open-Country Predators

Driving along sagebrush country roads in the morning hours, you might be lucky enough to spot a medium sized brown bundle of feathers with big imposing eyes. This is especially true if there happens to be fence posts lining the roadside. You would be witnessing a Burrowing Owl – an animal of the open sagebrush plateau and grasslands.

Burrowing Owls usually don’t burrow, although the male might modify a hole by scraping with his talons or on rare occasions dig one. They use abandoned ground squirrel, prairiedog, or other previously dug burrows. They will stand by the entrance but are quick to enter the security of the burrow when alarmed. If you wait, they will sneak back to the entrance to take a peek at their surroundings.

This owl stands 9 inches tall, has long legs, and big yellow eyes. It is a diurnal owl but will hunt when the moon is out. It kills by burying its talons in the victim’s back and then pecking vigorously at its neck. It will eat mice, voles, baby ground squirrels and rabbits, but rarely takes other birds. It does consume a large amount of insects such as grasshoppers and large beetles.

Both parents incubate the eggs (6 to 11) for a month and will bring food to the brood for 6 to 8 weeks. As the babies get larger, they will stand by the burrow’s mouth. A “cack-cack-cack-cack” alarm call by a parent on a nearby perch will send them scurrying back into the hole. The young are very vulnerable to predation and will hiss, like a snake, when threatened. The parents are also very intolerant of other species coming close to their burrow.

We have encountered this species sitting on fence posts when we drive the Yale road toward Heglar Canyon, or on the road to Milner by BLM land. This bird is migratory and we have observed them in the Imperial Valley of California in the winter. They seem to be abundant along the canals and alfalfa fields in the farming area south of the Salton Sea

On the alert on the edge of a hay field