Henry S. Fitch

Diverse and Contrasting Effects of Habitat Fragmentation

Different components of an ecosystem can respond in very different ways to habitat fragmentation. An archipelago of patches, representing different levels of fragmentation, was arrayed within a successional field and studied over a period of 6 years. Ecosystem processes (soil mineralization and plant succession) did not vary with the degree of subdivision, nor did most measures of plant and animal community diversity. However, fragmentation affected vertebrate population dynamics and distributional patterns as well as the population persistence of clonal plant species. The results highlight the dangers of relying on broad community measures in lieu of detailed population analyses in studies of fragmented habitats.

Ecological patterns of relative clutch mass in snakes

SummaryData on the relative clutch mass of snakes are summarized for over 100 populations. RCM was significantly lower in live bearing versus egg laying forms. We suggest that the longer reproductive season of viviparous snakes results in higher overall mortality compared to oviparous species; by reducing RCM, viviparous snakes may reduce this risk of mortality. Unlike lizards, no differences in RCM were found between categories of either escape behavior or foraging mode, possibly because detailed information on these behaviors are lacking for most snakes. In four populations examined, RCM did not vary among years. When compared to lizards, snakes demonstrate significantly higher RCM, perhaps owing to a more energetically efficient means of locomotion. Our data support the contention that RCM should be considered a separate and distinctive life-history characteristic of reptiles.

A Radiotelemetric Study of Spatial Relationships in Some Common Snakes

Radio transmitters embedded in silicone rubber in elongate, oval, smooth-surfaced packages 50 x 21 x 14 mm or a little larger, were forcefed to 67 snakes of eight species (a 68th snake had an abdominally implanted transmitter), which were then trailed on a day to day basis. Forty per cent of all snakes located had made no movement since the previous day. Average distances, in meters covered per day, were: 142, Pituophis melanoleucus; 51.3, Elaphe obsoleta; 44.7, Crotalus horridus; 28.5, Coluber constrictor; 10, Thamnophis sirtalis; 8, Agkistrodon contortrix; 7, Lampropeltis calligaster; 3.7, Natrix sipedon. Movements were irregular and erratic. For periods of 15-30 days the trailed snakes usually moved progressively farther from their starting points. Three displaced snakes exhibited no homing ability. One female N. sipedon made short, irregular movements typical of resident individuals. A displaced male A. contortrix made an unusually long movement the first night, then settled down to a pattern of short, irregular movements like those of residents. A displaced female C. horridus moved away from the release point but did not travel toward its place of origin approximately 10 km distant.

Natural History of the Racer Coluber constrictor

Natural history of the racer Coluber constrictor , Natural history of the racer Coluber constrictor , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Natural History of the Black Rat Snake (Elaphe o. obsoleta) in Kansas

Over a 15-year period, 359 black rat snakes were captured, mostly on a 750-acre area; because many were recaptured after marking, records totaled 516. The average emergence date was 16 April and 27 October was the average date for the end of the seasons activity. Calculated home ranges averaged 29 acres for males and 23 acres for females. Males are more inclined to wander, but in both sexes the tendency to remain within a familiar range is strong. Hatchlings appear in late summer or early autumn and range in snout-vent length from 290 to 368 millimeters; typical one-year-olds range from 500 to 650 millimeters. Sexual maturity is attained in the fourth year usually at a snout-vent length of a little less than 900 millimeters in males (which usually mature somewhat earlier) and a little more than 900 millimeters in females. Monthly gains in the growing season average 36 millimeters in the young of each sex. In the third or fourth year there is abrupt slowing, most marked in the females. Large adult males gain on the average a little more than three millimeters per month in the growing season. On the basis of observed growth rates more than one-fourth of the rat snakes recorded were eight years old or older, and some may have been more than 20 years old. The rat snake depends primarily on small birds and mammals for food, but takes an occasional frog, lizard, or snake. Birds are preyed upon chiefly in the nesting season; few adults are eaten. The red-tailed hawk is an important natural enemy; 577 instances of predation on rat snakes were recorded for this kind of hawk, but for other predators few records were obtained.

Comparison from Radiotracking of Movements and Denning Habits of the Raccoon, Striped Skunk, and Opossum in Northeastern Kansas

A comparative study of spatial relationships of the opossum ( Didelphis marsupialis ), raccoon ( Procyon lotor ), and striped skunk ( Mephitis mephitis ) was made on the University of Kansas Natural History Reservation, an area of deciduous woodland, brush and grassland. Thirty-nine animals, including 27 opossums, eight raccoons and four skunks, were each equipped with small radio transmitters and were trailed to their dens over periods ranging from 2 to 239 days. Each animal was found to use a series of dens and each well-situated den was used by many different individuals. Sometimes two or several different animals used a den simultaneously; on one occasion an opossum and a skunk were known to have used the same den simultaneously over a period of days. Whereas raccoons and skunks are somewhat social, opossums are generally solitary and instances of known co-occupancy could be attributed either to chance or to sexual attraction. Average occupancy of a den was 1.5 days for the raccoons and 2.2 days for both skunks and opossums. The average shift between successive dens was 1430 feet for the raccoon, 1359 feet for the skunk and 990 feet for the opossum. The most used dens were underground and were situated along a hilltop limestone outcrop. Raccoons often spent the day in trees, sometimes in cavities but more often in exposed situations such as on top of the platform of an old squirrel nest. Sign indicated that the underground dens used by all three species were chiefly the work of the striped skunk.

The Anolis Dewlap: Interspecific Variability and Morphological Associations with Habitat

TheAnolis dewlap is a highly specialized display organ that shows considerable interspecific variability throughout the genus. Differences among many species in dewlap lepidosis provide several characters that are taxonomically useful. There are more or less distinct gorgetal and sternal scale-row arcs that differ interspecifically in number of rows, as well as in number, shape and size of the scales. There are small, closely set granular scales, here termed apicals, at the anterior and posterior corners of the dewlap. Anolis dewlaps are generally bordered by enlarged, imbricate marginals of a variable number of rows. Besides scalation, other interspecific differences occur in color, pattern and size of the dewlap. Where seasonally dry climates limit reproduction to a short and concentrated annual breeding season, dewlaps are usually relatively large and brightly colored. In relatively aseasonal climates of tropical rainforests and cloud forests, dewlaps are often relatively small and, whereas some are brightly colored, others are a dull brown, tan or white. These differences in dewlap size are significantly correlated with another variable that is linked to seasonality of environmentssexual size difference (males are larger than females in seasonal environments). In some instances, there also may be compensatory development of bright colors in small dewlaps or large size in those that are dull colored. MANY genera of iguanid lizards have conspicuous and distinctive organs, colorations or behaviors developed for visual display; the anole dewlap is one of the most specialized of these and is unique in various respects. Although characteristics of color and pattern of dewlaps have often been used in species descriptions of Anolis and are commonly used by many field-workers as means to identify species, most other morphological characteristics of dewlaps have received little study. Rand and Williams (1970) studied dewlap variability among eight sympatric species of Anolis at a single locality in Hispaniola, and considered the differentiation as it related to the premating isolation of the species. On the mainland of Middle America, however, considerably fewer species of Anolis are sympatric at most localities, and therefore the potential for interspecific competition and hybridization is greatly reduced. Our previous observations of Anolis in Middle and South America have suggested that interspecific variation in several morphological characters of dewlaps may be associated with seasonality of habitat. These observations prompted this study of the associations of lepidosis, color and size of dewlaps with environ

A Radiotelemetric Study of Spatial Relationships in the Opossum

Habits of 27 opossums were studied by attaching small radio transmitters and trailing them on the University of Kansas Natural History Reservation in 1966 and parts of 1965 and 1967. Activity is normally nocturnal and during the day each animal stays in a den. Most of the 88 dens located were in underground cavities of hilltop limestone outcrops; others were among tree roots in cutbanks of gullies; relatively few were in miscellaneous situations such as hollow trees, old buildings, or burrows away from rock outcrops. The average sojourn at a den is 2.2 days and each opossum uses many different dens but returns frequently to each of several favorite dens. An adult opossum forages from its den over an area with mean radius of 620 m but tends to stay much closer to its den. Extent of movement and frequency of shift were not closely correlated with season or temperature. A newly independent, young opossum tends to stay within a relatively small area at first, and to extend its range by gradual stages. Of nine young opossums that were trailed, three were preyed upon by the horned owl.

Preliminary Experiments on Physical Tolerances of Eggs of Lizards and Snakes

In lizards and snakes the egg is a vulnerable stage in the life cycle with limitations that must often restrict geographic range or local occurrence of a species. Eggs of the rat snake, racer, ring—necked snake, Great Plains skink and five—linked skink were exposed in mixed groups to various controlled conditions of temperature and humidity to determine some of the differences between species in their ranges of tolerance. In atmospheres of 60 to 90% relative humidity eggs of all kinds tested lost water rapidly over periods of days and were short—lived. Mold contributed to mortality. At higher humidities survival was prolonged. At 97.5% relative humidity eggs dehydrated slowly but sometimes survived for several weeks and produced normal hatchlings. The small, thin—shelled eggs of ring—necked snakes deteriorated much more rapidly than eggs of the other species tested, and those of the racer were most resistant. In incubation media of decaying wood, loamy humans, crushed limestone and sand, with water content of 2 to 68%, eggs of all kinds tested gained weight by absorption of moisture and most eventually hatched. Gains in weight were gradual and were not proportional to the moisture content of the medium. For all species tested the eggs were eury—thermal with limits of tolerance near 41@?C and lower limits near the freezing point, but there were minor differences between species, and for the ring—necked snake the range of tolerance was several degrees narrower that it was for the skinks. For the egg, temperature is much less limiting than moisture.

Amphibians and Reptiles of the Rogue River Basin, Oregon

The region drained by the Rogue River includes parts of Jackson, Josephine, and Curry counties, in southwestern Oregon, and of Siskiyou and Del Norte counties in northwestern California. Roughly, it is bounded on the east, south, and north by the crests of the Cascade, Siskiyou, and Umpqua mountains. It comprises an irregular area having a maximum breadth of about 120 miles west to east and of perhaps half that distance from north to south. This area is possessed of varied climate and rough topography. The coastal belt supports dense forests of Douglas fir, coast hemlock, tan oak, California laurel, and Port Orford cedar. To the mouth of the Illinois River at Agness, for more than 40 miles the Rogue River runs through a deep gorge. The region of this gorge, and its counterparts on the tributary Illinois and Applegate rivers, is dry and rugged; Garry and golden oaks, manzanita, and buck-brush (Ceanothus cuneatus) are some of the plants most characteristic of the steeper slopes. A few miles west from Grants Pass the head of the main gorge opens out into a valley, most of which is under cultivation. The foothills around the valley include areas of dry, open grassland, as also areas of chaparral, oak, and madrone. At high altitudes this scrub type of forest grades into yellow pine and Douglas fir. Yet higher, discontinuous belts of Canadian and Hudsonian life zones partly surround the valley, forming more or less effective barriers to some species of amphibians and reptiles. During the 25 years of my residence in this region, I gained general familiarity with its fauna. However, no specimens were preserved and no field notes were written until the summer of 1932. In the summers of 1934 and 1935 I made collections and notes on nearly all the species, and trips were made to parts of the area not previously visited, notably along the lower course of Rogue River. Most of the specimens collected, representing all the species except Batrachoseps attenuatus and Contia tenuis have been deposited in the Museum of Vertebrate Zoology, University of California. Numbers given are as of the herpetological catalogue in the Museum, unless otherwise indicated. From time to time I have kept under observation in large outdoor cages many individuals of most of the species here discussed. In the following accounts it is my aim to summarize the geographic, zonal, and ecologic distribution of each form found within the area, and to include observations on its natural history. Specific localities are mentioned for rare species represented by few localities; but for common species represented by many records, these have been summarized in general statements. All localities mentioned may be found on the U. S. Geological Survey topographic maps or on national forest maps. 634