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THE common laboratory white rat is almost always the albino variety of the Norway rat (brown rat, Rattus norvegicus)1,2 and only exceptionally the albino variety of the black rat (Rattus rattus)3. The two species are morphologically similar, which makes it rather difficult to distinguish them. Nevertheless, there are qualitative characters which make distinction sure.

IN regard to the distribubution of the black rat (Mus rattus), your correspondent may be glad to know that this animal, spread over the States in early days, but has since been supplanted, as in England, by the brown rat (M. decumanus). Forty years ago the black rat was the only rat in South-west Ohio. About thirty years ago the brown rat drove him out. Some years later the same occurred in Illinois. I have been informed by one of my students living in Minnesota, that neither rat is known in and about the town of St. Cloud in that state, only one having ever been seen there, and that was killed on landing from a steamer. I have seen it stated that the black rat is still to be found in some localities in England, among them the White-chapel Docks.

RECORDS of the melanic form of Rattus norvegicus from various parts of the British Isles have been published since Thompson1 in 1837 first described it as a new species under the name of Mus hibernicus. There is very little information about the frequency of melanism at any time in the wild population, and it is therefore impossible to draw an accurate picture of changes taking place in the status of the two forms in recent years. The matter is of interest from an evolutionary aspect, and also from the point of view of rodent control, where, since it is necessary to distinguish between colonies of the black rat, R. rattus, and those of the brown rat, R. norvegicus, it is desirable to know of the existence and status of melanism in the latter species.

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.

MR. MIDDLETON'S letter in NATURE, vol. xix. p. 460, induced me to inquire whether the black rat still occurs in Dresden, the museum under my care possessing several specimens, which were procured on the spot several years ago. The streets where this rat then occurred being known to me, viz., Meissener-strasse, Alaun-gasse, Konigsbrucker-strasse, all on the right bank of the Elbe, in Dresden-Neustadt. I inquired in many houses, offering a relatively high reward for a specimen, but hitherto in vain. The museum possessing further a specimen from a place called the Schenkhubel, about an hour's walk from the town, in the direction of the last of the above-named streets, I had traps put there, but also in vain; only the brown rat, Mus decumanus, could be procured.

In these studies the Osborne-Mendel (O-M) rat has shown a significantly higher level of caries activity than the NIH Black rat (BR) whether caged with their own kind, or caged with O-M animals during the caries test period. The patterns of caries activity were also different in that activity in the BR was predominantly in the sulci, while activity in the O-M was divided between the sulci and the smooth surfaces. The hybrid animals exposed to an O-M mother or an O-M cage mate during the test period, developed somewhat more activity on the smooth surfaces than those not exposed. However, the level of caries activity of all hybrid animals was nearer that of the BR than the O-M. The causative factors for these differences have not been determined.

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

FROM Prof. Giglioli's letter in NATURE, vol. xx. p. 242, it appears that the black rat is more abundant and widely distributed in Italy than in England. I know of some half-dozen specimens having been caught from time to time in the city of London, and in November, 1876, a male about six weeks old was caught, which lived in confinement for two years and three months. It was mated with a tame white one, and they had two litters of young which were black, save the feet, tip of tail, and a small brush of pure white upon the chest.

PERHAPS some of the readers of NATURE may be able to throw some light on the present geographical range of the Black Rat (Mus rattus, L.). In the early part of 1877 some individuals of this species came on board the steamship Lady Frances either at Bombay or at Rangoon, but, as the captain believes, at the latter port. The animals multiplied on board the vessel, and in August last I had the pleasure of receiving from the ship a living specimen, which was at once forwarded to the Zoological Gardens in Regent's Park, where, I believe, it may still be seen. In a “Catalogue of the Mammals of the Sahara,” by my friend, Canon Tristram, F.R.S. (vide “The Great Sahara,” p. 385), the author states that the “Far el Kla”, as the black rat is called by the Arabs, “still maintains its position” in the Algerian Sahara. And I was yesterday presented by Mr. F. Donald Thompson, of Seaton-Carew, with a skin of Mus rattus from New Zealand. This example, like those from Burmah, was brought over by a vessel (the Trevdyan) which loaded grain at Lyttelton, in the province of Canterbury, New Zealand, where the rats embarked. In August, 1878, Dr. Sclater, F.R.S., was good enough to inform me that “Mus rattus has rather an extensive range over Europe and Western Asia”, and added, “I fear it would not be possible to state it very exactly”. But it is evident that the range of the species is much wider, as it is known to occur in North Africa, British India, and New Zealand; and it is also said, by Prof. Bell and Mr. Macgillivray, to have been carried to America and the South Sea Islands by ships. I should be glad to have further evidence as to its occurrence in Burmah, and it would be also desirable to know if it is found in the Malay Archipelago, China, Japan, or Australia. Dr. Peters, of the Zoological Museum at Berlin, assured me, in June last, that the species was extremely rare, if not actually extinct, in Germany, and showed me the only specimen in the fine collection under his care—an old and faded skin from Hanover. The animal lingers in one old building at Stockton-on-Tees, and there is clearly a possibility of its being reintroduced in many seaport towns through the agency of ships.

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

IT may interest the readers of NATURE to know that the black rat is very abundant and widely distributed in Italy and her islands. In the Central Collection of Italian Vertebrata which I have founded in the Florence Zoological Museum, I have a large series of specimens from no less than fifteen localities, viz., Domodossola, Casale, Florence, Radda, Arezzo, Castelfalfi, Lecce on the continent, Bastia (Corsiea), Cagliari (Sardinia), Castelbuono Madonie (Sicily), and from the islands of Elba, Pianosa, Montecristo, Giglio, and Lipari. On the smaller islands the larger M. decumanus does not exist at all, but elsewhere the two species live side by side. In the Florence Museum we have M. decumanus in the cellars, and M. ratius upstairs. This proves that the black rat is very far indeed from extinction with us; I should say that it is generally more abundant in Italy than its larger congener, at least such is my experience.

IT had been supposed for a long time that the ship or ‘black’ rat, Rattus rattus L., did not occur in sewers in Britain. There was a record from the sewers of Lima, Peru1, but no such records existed for the United Kingdom.

Apart from being against the law, illegal waste dumping also poses a threat to human health and to the environment. Solid and decomposing waste is an ideal breeding ground for a number of rodents, insects, and other vermin that pose a health risk through the spread of infectious diseases. The main objective of this study was to survey disease vectors and rodents for the presence of Leishmania sp. from illegal waste sites along the Istrian Peninsula in Slovenia and Croatia. The entomological and rodent survey was carried out between April 2011 and May 2013, at 12 locations, considering only illegal waste sites which consist of at least 2 m3 of garbage. A total of 119 specimens of Phlebotomine sandflies were collected. Five species were identified as follow: Sergentomyia minuta (48.7%), Phlebotomus perniciosus (30.3%), P. papatasi (13.4%), P. neglectus (5%) and P. mascitii (2.6%). Additionally, 173 small rodents were trapped at the same sites including following species: Rattus rattus (3.5%), Mus musculus (44%), Apodemus agrarius (27%), A. flavicollis (15%) and A. sylvaticus (10.5%). A geospatial analysis software ArcView was used to map the distribution of both vectors and rodents. Sandflies and rodents were screened using a molecular probe to amplify an approximately 120 bp fragment of the kinetoplast DNA (kDNA) minicircle for the detection of Leishmania spp. parasites. While not recorded in the tested sandflies, L. infantum DNA was detected in the spleen of one juvenile black rat (R. rattus). Despite few published records on Leishmania spp. infection in black rats, the addition of our record highlights the importance for further investigation into the frequency and distribution of such occurrences so that we may better classify the role of rodents as potential reservoirs of leishmaniasis in the Mediterranean basin.