deposition of opossum scats were at the bases of large trees, usually honey locusts or elms, near the animal's den. Accumulations of several dozen scats may collect in such situations. Often the opossums live-trapped were found to have deposited scats and many of these were saved for examination, although they were usually trampled, broken and mixed with earth and hair. Few scats were seen in the field throughout the summer. Their disintegration is rapid at that time of year because of the high temperature, frequent heavy rains, and abundance of dung-feeding insects. Scats were seen in greatest abundance in the fall, partly because the opossum population was then at its annual high point. During fall, wild fruits made up the greater part of the diet and were represented in almost every scat that was seen. Wild grape (Vitis vulpina) is an abundant woodland vine on the area and often forms dense tangles both in deep woods and in edge situations. Grape was the most abundant single item, and a large number of scats consisted exclusively of grape seeds and skins. In November and December opossums could be trapped most effectively by making sets in or near grapevine tangles where the animals were attracted by the abundant ripe fruits. The crops of wild grapes were especially heavy in 1948 (before live-trapping was begun) and in 1949, and scats containing them were noticed in those years especially. Opossums, too, were more numerous on the Reservation in 1948 and 1949 than they were in 1950, 1951, and 1952.

Hackberry fruit (Celtis occidentalis) was second to grape in importance and large numbers of scats were found to be composed mainly or entirely of the skins and seeds of this fruit. In the fall of 1951, these fruits were especially important and were the principal food source.

Wild plum (Prunus americanus) and wild crabapple (Pyrus ioensis) also are important in fall and winter and are present in many scats. In summer, blackberry, abundant on some parts of the Reservation, is an important food. Other wild fruits noticed in scats include those of cherry (Prunus virginiana) and climbing bittersweet (Celastrus scandens), and mast (acorn ?). In the fall of 1948, corn made up a large part of the contents of scats noticed. Crops of corn were grown on two fields of the Reservation in that year. In following years, corn was noticed less frequently in scats but still continued to be one of the important food items. Several cornfields adjoined the Reservation, and the scats containing the grain were observed mainly along the borders of these fields.

The crayfish is evidently the most important animal food, at least during the cooler half of the year when scats are seen in greatest numbers. Remains of crayfish were far more conspicuous than those of other invertebrates, and often made up the greater part of the scat. The sample of scats examined in the field, as noted below, are thought to be representative of the much larger number noticed but not examined in detail.

Sandidge (loc. cit.) found remains of cottontail rabbit in some of the stomachs he examined, but followed Reynolds (1945) in regarding these as carrion since the opossum was considered to be too inefficient a predator to catch and kill cottontails—prey approximating its own size and much superior in speed. Adult cottontails seem to be secure from opossum predation under ordinary circumstances. However, the opossum obtains some of its food by raiding the nests of small animals, including those of rabbits. At the Reservation, on May 21, 1951, at 9:00 P. M., distressed squealing of a rabbit was heard in high brome grass. Investigation revealed that a large male opossum had killed a young cottontail, weighing approximately 150 grams, and had started to eat it. This young rabbit, about the minimum size of young wandering outside the nest, evidently was pounced upon as it hid beneath the high grass.

Live-traps for mice, in lines or grids of 100 or more, often were set on the Reservation, and predators, including opossums, disturbed them on many occasions. Attacks sometimes resulted in release and escape of the trapped animal, and in other instances resulted in its being caught and eaten. In many instances identity of the predator could not be determined, but it is believed that such attacks by the opossum were relatively infrequent and inefficient. Steel traps set beside the mouse traps after consistent raids, to catch or discourage the predator, caught opossums on several occasions. These opossums usually had overturned mouse traps without opening them and when the trapped mouse was missing from the trap no evidence of its having been eaten was obtained. On other occasions raccoons were caught in the steel traps, and their raids were characterized by systematic and dextrous opening of the mouse traps and, frequently, by predation on the small mammals inside them.

Wire funnel traps set for reptiles along rock ledges also were often disturbed by predators, mainly skunks and opossums, both of which were caught on several occasions, when steel traps were used as a protective measure. The opossums often were attracted to the funnel traps by large insects such as camel crickets, grasshoppers and beetles, but also by trapped lizards including the skinks (Eumeces fasciatus and E. obsoletus) and the racerunner (Cnemidophorus sexlineatus). Both Sandidge (1953) and Reynolds (1945) recorded the five-lined skink (E. fasciatus) in opossum stomachs. On the Reservation this common lizard probably is one of the most frequent items of vertebrate prey of the opossum. Flat rocks a few inches in diameter frequently have been found flipped over; larger flat rocks and those solidly anchored in the ground often have been found partly undermined by opossums scratching away the loose dirt at their edges. Flat rocks similar to those found disturbed by opossums are the favorite resting places of the skinks, which, in cold or wet weather, are sluggish when beneath such shelters; this is especially true of female skinks that are nesting. The shape and size of some of the excavations suggested predation on skink nests. Other possible food sources in the same situation, in loose soil beneath flat rocks, include narrow-mouthed toads, lycosid spiders, beetles (mainly carabids such as Pasimachus and Brachinus) and occasionally, snails, centipedes and millipedes.

A pond, a little more than an acre in size, was a focal area for opossums and more were caught there than on any other part of the Reservation. Opossums that were trapped and marked on other parts of the Reservation were likely to be caught here sooner or later. Tracks in the mud showed that the edge was patrolled almost nightly by one or more opossums and this activity was especially noticeable when the pond was drying. Frogs were obviously the chief attraction inducing the opossums to forage there. Of the 8 kinds of frogs and toads breeding at the pond, the bullfrog (Rana catesbeiana), leopard frog (Rana pipiens) and cricket frog (Acris gryllus) were most abundant, throughout the season and especially when drying occurred. All three probably are important foods of the opossum locally.

Opossums were weighed in the field, with small spring scales of 2000-gram capacity, graduated in 25-gram intervals. Weights recorded were accurate within a margin of about 10 grams. After other data were recorded, the opossum was offered the hook at the base of the scale, and usually bit and held fast. Then it could be suspended off the ground and a reading taken.

When the same opossum was trapped two or more times within a few days, weight was usually found to fluctuate sometimes more than 200 grams, or more than 10 per cent of the animal's body weight. Opossums recaptured soon after their original capture and toe-clipping were generally found to have lost weight, reflecting the deleterious effect of marking by this method. The temporary laming of the animals prevented them from traveling as far or as fast as they normally would have; consequently they probably obtained correspondingly less food. They were also handicapped in digging, grasping and climbing. Nineteen such animals taken within a month of the original capture and marking, averaged 94 per cent of their original weights. The minimum was 82 per cent. Only 2 of the 19 had gained.

The stumps of amputated toes did not heal rapidly in opossums—contrary to experiences with many other kinds of mammals, reptiles, and amphibians also marked by toe-clipping. For many weeks the toes remained unhealed, sore and swollen. In several instances after periods of months the clipped toe stumps were unhealed. This was observed even in some of the opossums that were marked as pouch young and recaptured when grown to nearly adult size.

Some adult opossums trapped were heavier than the 2000-gram capacity of the spring scale usually used in the field, and no definite weights were recorded for most of these animals. Some of them that were caught near the laboratory were brought there for weighing.

Even within the same age- and sex-group at any one time, opossums varied widely in general condition and in weight. Some were emaciated and sickly in appearance with sparse, ragged pelage, while others were in excellent condition, fat and with thick, glossy pelage. Seasonal trends are partly obscured by these differences in individuals, by the tendency to lose weight in those recently marked, and by the irregular fluctuations that occur in each animal.

Figure 5. Weight changes in opossums live-trapped; lines connect successive weight records of the same individual, showing, in most, a downward trend throughout the winter and early spring, and an upward trend in late spring.

The few opossums caught in summer were thin and appeared to be suffering from infestations of ectoparasites, especially chiggers (Eutrombicula alfreddugesi) and ticks (Dermacentor variabilis). Those trapped in October and November were mostly fat and in good condition. For individuals caught at different seasons, maximum weights were generally recorded in these two months. The maximum weight record of the study was one of an adult male weighing 5000 grams on December 23, 1950. The weight records of this individual were more complete than most and are recorded below to illustrate seasonal trends for adults. May 10, 1950, 1925 grams; May 14, 1830 grams; May 17, 1940 grams; November 5, 4540 grams; November 28, 4540 grams; December 23, 5000 grams; February 18, 1951, 3300 grams; March 6, 3080 grams; March 28, 3080 grams; May 28, 3080 grams; June 18, 2620 grams.

Of opossums that were trapped alive, the weight ranged from the maximum of 5000 grams to a minimum of 126 grams. The maximum in males was higher than in females. In fall, three rather poorly defined age-size groups were discernible in each sex: adults more than a year old and including all the largest individuals; large young born late the preceding winter and approaching small adult size; smaller young born in early summer and still less than half-grown. After November, young cease to gain, or gain slowly and irregularly through the winter and spring and adults tend to decline in weight, as food becomes scarce and frequent fasting is enforced by cold or stormy weather. The smaller young probably are subject to drastic reduction in numbers as a result, directly or indirectly, of severe winter weather. Many of these smaller young, weighing considerably less than 1000 grams, did not survive overnight when caught in live-traps in cool autumn weather, whereas adults and well-grown young generally survived exposure even for several successive nights in various extremes of weather conditions.

Hartman (1928:154) stated that there were at least two litters of young per year in the southern states with a small percentage of unusually fecund females producing a third litter. Lay, in eastern Texas, concluded (1942:155) that "The present investigation substantiates Hartman's deduction of two litters being normal, but fails to disclose any evidence of a third litter." He found females carrying young in the pouch only within the seven-months period January to July with definite peaks in February and June, and stated that second litters appear in the pouch from early April to as late as May 20 to 23. Reynolds (1945:362) found that the breeding season in central Missouri in 1941 and 1942 began about the first of February, with known or calculated birth dates of 42 litters rather evenly distributed throughout the periods February 12 to April 2, and May 16 to June 4. Eight of these females had given birth to young between March 16 and April 2, approximately six