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We used radiotelemetry to determine habitat use by 11 black rat snakes (Elaphe obsoleta obsoleta), five fox snakes (Elaphe vulpina vulpina) and four blue racers (Coluber constrictor foxii) at the Middle Fork Fish and Wildlife Area in east-central Illinois in 1997 and 1998. Black rat snakes selected forested habitats, whereas fox snakes and blue racers selected old fields and prairie restorations. No consistent association with forest- field edges was noted for any species. Fox snakes and blue racers were primarily terrestrial, whereas black rat snakes used all categories of vertical space but were primarily arboreal. Snakes were tracked to three hibernation sites, including an abandoned railroad trestle and two abandoned trash and construction-material dumps. These data provide the first comparative, quantitative descriptions of habitat use for these species in sympatry, and one of the few descriptions of hibemacula in a region dominated by row-crop agriculture. Due to their secretive behavior, snakes are difficult to study in the field and many impor- tant features of their ecology and natural history are not well known (Seigel et al., 1987; Seigel and Collins, 1993). Snakes also are frequently considered vermin and often indiscriminately killed by humans (Dodd, 1987; Greene, 1997). Because many species of snakes are declining in numbers (Dodd, 1987; Greene, 1997), it is im- portant to identify and protect critical habitats and landscape features relevant to their conser- vation. In temperate regions, sites used as hi- bemacula may be particularly important to the persistence of populations of many species of snakes (e.g., Prior and Weatherhead, 1996; Bur- brink et al., 1998). However, little information exists about habitat selection and sites used as hiberacula by snakes in agricultural regions of the midwestern United States.

In long-lived birds, reproductive performance is considered to increase with breeding experience, influencing site and mate retention. However, breeding success also depends on external factors. We therefore increased experimentally the breeding success of a population of White-chinned Petrels Procellaria aequinoctialis that had been suffering from black rat Rattus rattus predation. Thus, we were able to control for intrinsic and extrinsic factors when studying relationships between reproduction and fidelity in this long-lived and faithful species. Rat poisoning led to a significant increase of breeding success, site and mate fidelity. Breeding success increased with individual experience and breeding failure affected burrow fidelity significantly, but only during the period when rats were not poisoned. After rat poisoning had started, birds were more likely to retain their burrows as they became more experienced, but breeding success and experience had no effect on mate fidelity in either period. Although White-chinned Petrels seemed to change burrow or mate in order to improve their breeding success, the major factor causing changes was disturbance caused by rats rather than breeding failure per se. Variations in mate fidelity appeared to be merely a consequence of variation in burrow fidelity. Our results disagree with most studies on long-lived and faithful species. Therefore, controlling for both intrinsic and extrinsic factors is desirable, and comparisons within and between populations should be combined whenever possible when studying life-history traits.

Suitable over-wintering habitat is critical to the survival of snake populations at higher latitudes. The identification and protection of traditional, communal hibernation sites (hibernacula) is important for the conservation of threatened species, while the assessment of hibernacula availability may help determine the extent to which population distributions are limited by habitat suitability. In this paper, we quantified surface habitat characteristics of 10 hibernacula and the composition of basking trees used by a threatened population of black rat snakes (Elaphe o. obsoleta) at the northern limit of the species' range. Hibernacula were typically situated on relatively rocky, south-facing slopes. The co-occurrence of these features was sufficiently unique as to distinguish hibernacula from (1) a series of random sites, but not from (2) a set of intuitively identified "potential hibernacula" in the surrounding landscape. This implies that additional requisite elements (e.g., underground structure and micro-climatic conditions), which we were unable to quantify, set actual hibernacula apart from sites that appear to be otherwise suitable (i.e., "potential hibernacula"). Basking trees found at hibernacula tended to be relatively large and decayed or dying with numerous cavities. Unused trees exhibiting these characteristics were also available at both random sites and potential hibernacula indicating the suitability of those sites for basking. Our results suggest that rat snake hibernacula cannot be predictably located by simply searching for key surface habitat features in the landscape. The current data are equivocal as to whether or not this most northern population is limited by the availability of suitable over-winter habitat since the possibility that essential subterranean features of hibernacula are limiting remains to be tested. We recommend the continued use of radio-telemetry to identify and protect additional hibernacula, the preservation of basking trees at known hibernacula, and further research to determine the internal structure and micro-environ- ments of hibernacula.

Black rat snakes (Elaphe o. obsoleta) are important predators of nesting birds and small mammals in fragmented landscapes. Thus, we used radiotelemetry to study movements of 32 black rat snakes at Remington Farms, Maryland, during 1988-89 to determine potential ways to minimize their depredations, Yearly home ranges were similar (P > 0.05) for males and females (x ± SE) (convex polygon, 9.49 ± 1.01 ha; 95% harmonic contour, 10.52 ± 1,24 ha), but males covered more (P < 0.05) of the home range earlier in the spring. Snakes were familiar with habitat features within their home range, returning to the same areas after prolonged absences. Snakes used forest edge, residential, hedgerow, and herbaceous/brush habitats more (P < 0.05-0.001) than expected by chance

Four albino black rat snakes, Elaphe obsoleta obsoleta, one tan or xanthic in color and the other three completely amelanistic, were subjected to various breeding combinations to determine their genetic relationships. They were found to represent three distinct forms of albinism. Skin biopsies from the three forms were subjected to the dopa reaction, and biopsies from two of the forms were examined by frozen section. The two amelanistic forms were found to be non-allelic and to have biochemically different types of albinism, one tyrosinase-positive and the other tyrosinase-negative. The hypomelanistic or xanthic albino form was found to be tyrosinase- positive, allelic with the amelanistic tyrosinase-positive form, differing quantitatively in the bio- chemical defect in melanogenesis. The occurrence of albinism in Elaphe obsoleta is documented. Hensley (1959) surveyed the known records of albinism in North American reptiles and amphibians, and listed 12 records for the species. This list included many that had been reported in scattered references plus some that had not been recorded previously. Two of the records were from Texas and presumably were of the subspecies lindheimeri, but the remaining 10 were from within the range of the nominate form. No similar survey has been published since 1959. However, albinism is a regular though uncommon mutation that has been found in every vertebrate form of which a sufficient number of individuals have been observed, and sporadic albino specimens continue to be found as more individual snakes are collected. The common name of Elaphe obsoleta obsoleta is black rat snake. However, the individual snakes are by no means always uniformly black, with differences not only in different parts of the range but also individual differences within various parts of the range. The dorsal scales are generally black, but the skin between many of the scales is often of a much lighter color: white, yellow, orange, or red (Conant, 1958). There are frequently lighter shades at the edges of many of the scales. This, in combination with the lighter shades between some of the scales, results in considerable variation in the appearance of individual snakes. The chief variation is the persistent visible trace of the juvenile pattern still present in many adult snakes. This may be visible at all times, but is especially noticeable if the scales are distended for any reason, such as the recent ingestion of a large meal. The juveniles are strongly patterned dorsally with dark blotches on a pale gray background. They darken rapidly with age and some, most, or virtually all of the juvenile pattern is gradually obscured by black. Individual adult albinos of this species also are not necessarily identical. A typical one (PI. 1) has a yellow-tinged white background with dorsal blotches that are generally some shade of yellow, tan, peach, or red. The blotches may be barely discernible as a light pink or tan, they may be quite conspicuous, or may be absent, resulting in an essentially white snake. The eyes have a gold or pink iris with a red pupil, and the tongue is also red. Preserved specimens do not give an accurate

The Scarcity of Rats and the Black Death: An Ecological History The black rat (Rattus rattus) is credited with causing the Black Death epidemic of 1347 to 1352 that killed one quarter to one third of Europe's population. But this supposed role of the rat may not be justified, although the claim is made in standard epidemiological texts, in history texts, and in countless rat control pamphlets. The Black Death has been analyzed in terms of bacteriological, epidemiological, and transmission factors, but it has never been carefully scrutinized as a rodent-related outbreak. This research note examines the history of rats in northern France and in England using current knowledge of the ecology of rodents and of rodent-borne diseases to evaluate the involvement of Rattus rattus in the Black Death. Writers have assumed, based on recent epidemics of plague, that rats were important.1 The scope of this research note is limited, except for some introductory or explanatory statements, to the possible role of rodents in the Black Death. Little is said about epidemiological, bacteriological, or clinical aspects and nothing about sociological or political aspects.

Behavior, growth and age of black rat snakes under natural conditions were investigated by mark-recapture methods at the Patuxent Wildlife Research Center for 22 years (1942-1963), with limited observations for 13 more years (1964-1976). Over the 35-year period, 330 snakes were recorded a total of 704 times. Individual home ranges remained stable for many years ; male ranges averaged at least 600 m in diam and female ranges at least 500 m, each including a diversity of habitats, evidenced also in records of foods. Population density was low, probably less than 0.5 snake/ha. Peak activity of both sexes was in May and June, with a secondary peak in September. Large trees in the midst of open areas appeared to serve a significant functional role in the behavioral life pattern of the snake population. Male combat was observed three times in the field. Male snakes grew more rapidly than females, attained larger sizes and lived longer. Some individuals of both sexes probably lived 20 years or more. Weight-length relationships changed as the snakes grew and developed heavier bodies in proportion to length. Growth apparently continued throughout life. Some individuals, however, both male and female, stopped growing for periods of 1 or 2 years and then resumed, a condition probably related to poor health, suggested by skin ailments.

SUMMARY (1) Age- and sex-dependent foraging strategies were documented for the black rat, Rattus rattus Linnaeus, in the Galapagos Islands, Ecuador. A detailed analysis was made of the stomach contents of individuals from four breeding and four non-breeding populations. (2) Percentage of animal food in the stomach was negatively correlated with body length of rat in all six populations with young, growing individuals; the correlation was significant in four of the six cases. (3) In one population where three food types comprised more than 80% of the diet, the proportions of these foods in stomach contents shifted with increasing size of rat. As body size increased, animal food and Miconia robinsoniana berries comprised progressively less of the diet, while Blechnum sp. rhizome increased in importance. (4) Miconia robinsoniana berries were eaten by all individuals in one population; however, consumption of the berry skin increased with body size, while the extent to which the seeds were chewed decreased through increasing size classes of rats. (5) Solanum nodiflorum berries were eaten only by mature rats in three different populations. Size-dependent responses to several other foods were also found. (6) In one breeding population mature females ate significantly more animal food than did mature males. (7) These within-population feeding differences indicate the need to consider nutritional and toxic factors in analyses of foraging strategies.

ABSTRACr.-From late May to mid-September 1982 we investigated habitat selection by black rat snakes (Elaphe o. obsoleta) at the Queen's University Biological Station in eastern Ontario. We implanted radio transmitters in 4 male and 3 female snakes and used their daily positions as habitat sampling points. We also sampled the available habitat using randomly selected points. We located the snakes 472 times (>90% success) which produced 107 habitat sample points. All snake sample points were separated into active or inactive based on the length of time the snake remained in that position (less than or greater than 7 days, respectively). During the bird breeding season black rat snakes showed a preference for field habitat although in both the field and deciduous forest the snake points were significantly clustered along the habitat interface. Following the bird breeding season, field and deciduous forest habitats were used in proportion to their availability and the preference for the ecotone was no longer found in field samples. We found only limited evidence of non-random habitat use within habitats with regard to both plant species composition and vegetation structure. Inactive sites were diverse but all were located on the forest-field interface, had open exposure to direct sun and provided shelter for the snakes. We suggest from these results that ideal habitat for black rat snakes is a small scale mosaic of field and forest and that their disappearance from other parts of their range in Canada may be related to the disappearance of such mosaics due to land clearing for agriculture.

The cosmopolitan black rat (Rattus rattus) has been introduced to several islands of the Galapagos Archipelago, Ecuador, where it has become established in all vegetated habitats. The foraging behavior of this ecologically versatile species was studied through detailed analysis of stomach contents of rats trapped in four very different Galapagos habitats: thorn scrub, savanna, montane scrub, and montane forest. Plant foods comprised an average of 80 percent of stomach contents; however, animal food occurred in at least 81 percent of the rats in each population, and R. rattus reproduction was correlated with a high level of animal food in the diet. Although the rats fed on an extremely broad range of plant and animal foods, they were very selective feeders, discriminating among plant species and among parts of plants. Fruits and seeds were preferred foods, and in most cases the seeds were destroyed. These introduced rodents are probably having many severe effects on the Galapagos flora and fauna.

On 14 April 1979, at 0930 CST, a black rat snake (Elaphe obsoleta obsoleta) was observed rolling down a leaf-strewn slope along the Upper Jack's Fork River in Texas County in south central Missouri. Upon closer inspection a grayish bat was observed among the coils of the snake. We began monitoring the struggle between the two animals and recorded the event on film. Although the bat was not identified at the time, a distinct keel was observed on the calcar in one of the photographs. Given the fur coloration, the physical characteristics of the foot and the calcar, and the geographic location, it is probable that the prey of the black rat snake was an Indiana bat (Myotis sodalis). The bat was alive and struggling when first observed. From 0930 to 0932 CST the rat snake continued to constrict its prey. At 0933 CST, the bat appeared to be dead. The snake consumed the bat head first, a process that took nine minutes, with the membraneous wings of the bat being the last body segments to be devoured. The entire event spanned eleven minutes. The rat snake remained stationary for six more minutes, and then crawled into the leafy cover at the base of a tree. The encounter between snake and bat apparently had begun further up the slope since our first sighting was the movement of them rolling downhill. The two animals were approximately ten meters from numerous rocky outcroppings and 100 meters from a cave entrance. The timbered hillside contained several large dead trees. In summer, Indiana bats roost under loose bark and in hollows of trees (Humphrey et al., 1977), but some males spend the summer around hibernacular caves (Hall, 1962; Myers, 1964). Based upon this information and the knowledge that black rat snakes are both arboreal and enter caves, we speculate that the bat was hibernating or roosting in one of the suitable retreats. Because of the probable torpid condition of the bat, it was readily available prey for the snake. Several animals are known to prey upon bats. A leopard frog (Rana pipiens) captured and consumed a Myotis (Barbour and Davis, 1969). Rat snakes have captured bats in caves in Kentucky (Barr and Norton, 1965) and in Kansas (Collins, 1974). This paper documents a black rat snake effectively preying upon an Indiana bat in Missouri.

THE history of Rattus rattus and of R. norvegicus in this country is familiar to most zoologists, and only a few words need be said on the subject here. The black rat (R. rattus) is believed to be an alien which first reached our shores some time in the Middle Ages, a common suggestion being that it was brought back from the east on the ships of the Crusaders; at any rate it was an established and numerous member of our fauna for several hundred years, and the only species of rat existing in Britain. The brown rat (R. norvegicus) is an alien which is known to have appeared for the first time in Britain about the beginning of the eighteenth century. (Regarding the reported occurrence of bones of R. norvegicus in deposits at Kilgreany Cave, Ireland (5), Dr Wilfrid Jackson has written to me: " The upper levels were loose and somewhat disturbed, and I think the brown rat is a fairly recent intrusion there.") This is a larger animal than the black rat and more adaptable generally, and there seems little doubt that it was responsible for the complete disappearance of the latter from most parts of the British Isles. In many districts the black rat had been driven out before the end of the eighteenth century, though it survived, in dwindling numbers, in some inland places till about the middle of the nineteenth or later (6). During the latter

The rat population of Houston is different from that of any other American city, as far as known to the writer, in that from 35 to 40 per cent. of the city rats belong to the species Epimys alexandrinus, the roof rat. In other American cities, including the neighboring cities of Galveston, Beaumont and New Orleans, the roof rat constitutes less than 5 per cent. of the total rat population. The wharf or Norwegian rat, Epimys n'orvegicus, constitutes about 60 per cent. of the total number in Houston, whereas the true black rat, Epimys rattus, is rare, probably less than 1 per cent. of the total. This rat is commonly confused with melanistic examples of the wharf rat, which are rather common, so that the statistics usually give a higher percentage of Epimys rattus than is actually true. A considerable number of rats, probably between 1 and 2 per cent., though resembling roof rats in their graceful form, showed the coloration of wharf rats, and had a tail and ears which were intermediate between the two species. Whether these rats should be looked upon as a distinct species, or, as seems more probable, as intergrades between norwegicus and alexandrinus, has not been determined. The most interesting parasitological fact brought out by the examination of these rats is the common occurrence of Acanthocephala of the genus Moniliformis (Travassos 1915). Up to the present time these worms have been reported from the United States only in three instances. Ward in 1917 described these worms from a squirrel in Illinois. He considered his specimens as belonging to a species distinct from the Old World form and named it Hormorhynchus (-Moniliformis) clarki; a full description of this form has not yet been published. Worms of the same genus were previously reported by H. C. Chapman (1874) and by Stiles and Hassall (1984) from Sciurus vulpinus and Sciurus niger, respectively. Dr. Van Cleave has informed the writer that he has specimens of Moniliformis from Oklahoma also. Although the full statistics are not yet available, the percentage of adult Houston rats which are infe,cted is approximately 10%, the percentage of infected E. alexandrinus being higher than that of