Part 4

Blue racers that were recorded on more than one occasion were rarely caught again at the original location. For different individuals, distances between capture points ranged from zero up to a little more than three-fourths of a mile. The area of concentrated study was a mile and a half in greatest diameter; there was scant opportunity for capturing racers that moved greater distances. Even those that moved as far as a mile would have passed beyond the boundaries of the study area in most instances. Many of the marked racers that disappeared from my records probably moved beyond the limits of the study area. Nevertheless, in the great majority of instances, the distances between successive capture points for the same individual were relatively short, indicating that each racer tends to remain permanently in a restricted area.

Most captures were made in the type of grassland or brush that provides favorable habitat for the racer during the season of

## activity, but many other captures were made in woodland along the

rock ledges where the snakes come to hibernate. Four different types of movement may be recognized: 1) those in the rock ledge area where hibernation occurs; 2) those between the area where the summer is spent and the hibernation ledge--an actual small scale seasonal migration which takes place in spring and autumn--3) those within a home range, which are part of the day-to-day activities of the racer, and, 4) wandering movements by which the racer shifts its activities, perhaps permanently, from one area to another. In the records of any one snake these different types of movements cannot always be sorted with certainty. Each type will be discussed separately.

Relatively few movements along the ledges were recorded. It seems that having migrated to a ledge, the racer promptly finds its hibernaculum and retires for the winter. In spring there is equally prompt scattering of the emerging racers, which no longer find the ledge attractive. Most recorded movements along the ledges were short. Of 76 movements, nine exceeded 1000 feet, and only four others exceeded 500 feet. Most of the shorter movements were recorded within an autumn season, but several were recorded after the lapse of one or more seasons of activity. The longer movements were as follows: 1250 feet after 8 seasons (male); 1300 feet after three seasons (female); 1600 feet after one season (female); 2000 feet after one season (female); 2280 feet after seven seasons (male); 2200 feet in same season (female); 2410, 2600, and 3200 feet, each after one season (all males). The trend of these records suggests that the tendency to return year after year to the same hibernaculum is not strong; after using one for a period of years, the racer may abandon the stretch of ledge and, starting out in the opposite direction from its summer range, find a new hibernaculum as much as half a mile from the old one. Records of distances between capture points on the ledges for individual racers are shown in Fig. 12.

A total of 124 movements between summer ranges and ledges were recorded, and the distances averaged 1309 feet--approximately a quarter mile. Some racers living in hilltop fields may have had home ranges that included rock ledges, or at least were adjacent to them. In such instances no seasonal migrations would have been necessary to reach hibernacula in the autumn and summer ranges in the spring. Several short movements--100 feet, 150 feet, and 200 feet--can be explained on the basis that home ranges and hibernation ledges overlapped or were near at hand, but most of the movements were longer. The longest movement was 4020 feet, after a lapse of four seasons. Twenty-four movements exceeding 2000 feet were recorded. For these the intervals between captures averaged more than double the time for the remaining movements, indicating that the longtime permanent shifts were involved in many instances.

[Illustration: Fig. 9. Histogram of movements of blue racers between hilltop rock outcrops used for hibernation, and summer habitat on the Reservation and Rockefeller Tract. Movements of females tend to be somewhat shorter than those of males.]

For all the racers living in bottomland, ranges were separated from ledges by areas of wooded hillsides averaging approximately 700 feet across. These relatively unfavorable areas had to be traversed in the course of the semi-annual migrations. Even some of the racers that lived in hilltop fields apparently crossed wooded slopes in order to reach distant hibernation ledges, or else each reached the ledge by a roundabout route although it could have found a ledge much nearer its summer range. For the 124 ledge-to-field and field-to-ledge movements, the median distance was 1030 feet. The sexes were almost equally represented in this sample but the average distance for the 55 males--1425 feet--notably exceeded that for the 69 females--1220 feet. These movements are shown in Fig. 9.

McCauley (1945:76) in Maryland described what seemed to be incipient territoriality in a large male racer that remained several hours in a small area, crawling about conspicuously with head raised, seemingly on patrol. When an even larger male racer intruded, the first one aggressively drove him away, but neither paid any attention to a king snake that was also on the area. Other authors have noted the attachment of a racer to a small familiar area. Conant (1938:53) wrote that many of the racers he saw sought shelter in definite retreats. One of these racers was seen resting on top of a brush pile four times in a single afternoon, and each time it followed the same route to the same inaccessible spot beneath the brush.

My own observations do not bear out the idea that racers maintain regular territories, since several males may be present within a small area, even in the breeding season. Hostile behavior between males has not been observed by me under natural conditions, and in confinement has been seen only in instances of self defense. Like the racer Conant observed on a brush pile, individuals may linger in the vicinity of a favored shelter or foraging area for periods of hours, but such associations are ephemeral, and soon the snake moves on. In a uniformly favorable habitat a racer may cruise about freely in tall grass or brush. Individuals that I have attempted to follow, after flushing them or releasing them from traps, often covered distances of 100 to 300 feet within periods of a few minutes before I lost them. In such instances I maintained sufficient distance between myself and the snake so that the latter was not actively escaping. Probably the snake was not aware of pursuit in most instances, although I was able to glimpse it through the stems of grass, weeds, or shrubs, or was informed of its course by the swaying tops of grass and other vegetation.

For many of the racers captured over periods of years it was possible to plot "minimum home ranges" in the areas that they occupied. One caught 12 times in five consecutive years will serve as a typical example. There were seven locations involved; three captures were made at one point and two captures at each of two others; the other five locations were each represented by a single capture. One of the seven locations was for a capture made at a rock ledge in October, and hence can be eliminated from considerations of home range. The other six locations are based upon captures made from late May to early August, and they form a rhomboid pattern, with three locations in alignment on one side and two others inside the quadrangular figure formed by the five outlying points. Obviously such a group of records gives some idea of the location and extent of the snake's activities but the information is far from complete. As shown by Odum and Kuenzler (1955), a much larger series of records, usually several dozen, with eight or more marginal locations, is necessary to illustrate even an approximation of the actual home range. Under the conditions of my study such a series of records was unattainable. Few if any of the racers recaptured had more complete series of records than the one mentioned above.

For 20 racers the records were sufficiently numerous and well distributed to permit plotting of minimum home ranges. One of these ranges was hexagonal, nine were pentagonal, eight were rhomboidal and three were triangles. In four instances the area encompassed was broken by woodland, indicating that the home range comprised two or three disjunct segments. In all instances the smaller segments were triangular. The 20 minimum home ranges averaged 6.6 acres (3.2 to 12.8). The 15 ranges of males averaged 7.3 acres, whereas the five ranges of females averaged only 4.5 acres, but the sample is too small to be relied upon for differences in the sexes.

[Illustration: Fig. 10. Movements of blue racers within or between areas of summer habitat on the Reservation and Rockefeller Tract. The trends are much alike for males and females.]

In an earlier publication (Fitch, 1958:73) I discussed an alternative method for determining size of home range in animals that move about freely within a chosen area, not having their movements restricted by attachment to a specific home base. Ordinarily any two records of the animal within its home range will be separated _on the average_ by a distance equal to half the diameter of the area. Assuming that home ranges in general tend to have a circular shape, except as restricted by limiting environmental factors, the area can be easily computed from the average recorded movement--the home range radius. It is necessary, of course, to have a sufficiently large number of records of movements to obtain an average that is statistically reliable.

A major problem is that of recognizing movements that involve an extension of the original range or a shift away from it to a new area. A few exceptionally long movements were recorded. If these are included in the computations of home range, they greatly increase the average distance, probably introducing error. Also, the number of exceptionally short movements was greater than might have been expected if all locations of capture are at random to each other. In some instances a racer newly released may have blundered into the same trap again, or into the trap at the opposite end of its drift fence. In other instances traps may have been so strategically situated with respect to preferred travel routes that they caught the same snakes repeatedly. In still other instances, the range of an individual might have been mostly outside the study area, with only one end or corner overlapping the trap sites.

A total of 471 records for consecutive captures in field areas is available, 305 for males and 166 for females. In 20 instances successive sites of capture were the same and movement was recorded as zero. Of the 471 records, 207 involved a relatively long time span, including at least one hibernation period; the remaining 264 were based upon successive records within the same season of activity. The trends were much the same in the records involving a longer time span (up to four years) as in those records involving captures made in a single season, but for the longer periods there were some exceptionally long movements, and relatively few short movements of less than 100 feet.

Records of male racers and those of females were used for separate computations. For each series, the ten per cent of movements that were longest and the ten per cent that were shortest were eliminated from consideration in calculation of the average distance between points of capture. For the remaining 244 records of males an average movement of 595 feet was calculated, and for 132 records of females an average movement of 574 feet. These distances, if accepted as typical home range radii, would represent home ranges of 26.3 acres for males and 23.8 for females. In an earlier discussion of spatial relationships in the racer (Fitch, 1958:119), based upon relatively scanty data, I estimated the home range to be approximately 23 acres in males. But with only nine records for female racers I calculated the home range to be 9.7 acres.

The disparate figures obtained from plotting minimum home range and from calculating average home range radius are not irreconcilable, since a minimum home range based on only four or five points would ordinarily include only a fraction of the actual range. Distances up to 1500 feet are included in the calculation of home range. It seems that home ranges often have a diameter of this magnitude or a little larger, although the estimated average diameter is 1140 feet. Home ranges probably most often deviate from circular shape to form an ellipse, with one diameter markedly exceeding the other. Woodland, water, roads, buildings, or cultivated fields, or other areas that are unfavorable or uninhabitable often form the boundary of a home range and influence its shape.

Many of the longer movements constituted clear-cut shifts in range. In one exceptional instance a large adult female captured in the northeastern part of the Reservation on June 22, 1950, was released 21 days later at a point 3900 feet southwest of the place of capture. On May 27, 1960 she was caught within 600 feet of the original location, seemingly having made a homing movement. Among the nine racers recorded to have made longest movements (exclusive of those movements made to or from hibernacula) four were recorded also to have made later long movements in the reverse direction, probably returning, each to its original home range, although in every instance the return movement was somewhat less than the original. A female of two-year-old size when first captured on September 2, 1957, was recaptured 3100 feet southeast on May 10, 1958. On August 7, 1959, she was recaptured again 2400 feet from the second location in the direction of the original capture. Similarly, in a three-year-old female a shift of 2730 feet was recorded at the second capture after 21 months, and at the third capture 14 months after the second, a return trip of 2360 feet had been made. A second-year female made a trip of 2640 feet between May 17 and October 1, 1960; by May 1961 she had returned 2000 feet to the vicinity of her original capture. From one year to the next an adult male shifted 2450 feet; after another year he had moved back 1550 feet. Most of the longer movements recorded were those between home ranges in fields and hibernacula along ledges, but in this class of movements, distance was somewhat proportional to elapsed time. For 59 such movements exceeding 2000 feet the average was 3.1 years, whereas for 114 field-to-ledge movements of less than 2000 feet, average elapsed time was 1.6 years. This trend suggests that over periods of years a racer is likely to shift its range or its hibernaculum or both.

[Illustration: Fig. 11. Map showing home ranges of five blue racers, as indicated by numerous captures in successive summers, in small valley where Reservation headquarters are located, and spatial relations of their hibernacula, as represented by points of capture along hilltop limestone outcrops. In spring and autumn, traveling to and from hibernacula, the snakes migrate across wooded slopes. Each "minimum home range" is enclosed in a dotted line, and a distinctive symbol is used to show successive points of capture for each snake.]

[Illustration: Fig. 12. Map of 600-acre area of Reservation and Rockefeller Tract, including parts where field study was most concentrated, showing movements of the 20 blue racers recorded to have shifted over the longest distances. The figure following the sex sign of each individual indicates number of months elapsed between the captures at the localities represented by the dots.]

Average elapsed time between captures was 7.7 months. In the 471 field-to-field movements recorded, 53--slightly more than eleven per cent--exceeded 1500 feet and can reasonably be considered shifts of home range. The average elapsed time between captures for this group of snakes was 9.5 months. The evidence suggests that, even in an area of favorable habitat, somewhat more than ten per cent of the racers in a population annually shift their home ranges somewhat, but that many stay in the same home range for periods of years or perhaps throughout life.

Shifts in range were especially noticeable where availability of suitable habitat underwent seasonal change. Along the north edge of the Reservation, prairie adjoined cultivated fields where grain or hay was grown. Until late May, the cultivated crops made little growth and the fields were almost bare. They provided insufficient shelter for the racers, which tended to keep to the prairie, where old grass of the previous year's growth furnished them with ample cover. Later in the season, crops, of oats, wheat, and alfalfa constituted suitable cover for the racers, and many of them shifted their ranges to the cultivated fields, but corn and milo crops were much less adequate for their needs. After harvesting of crops, cover in the fields was again inadequate for the racers' needs, and they tended to retreat to edge situations, or to adjacent prairie.

Food Habits

_Methods of Obtaining Prey_

The racer hunts by stealth, but actively, obtaining its prey by keen eyesight and swift movements. Wright and Bishop (1915:160) wrote that because of its great speed it can catch anything that moves on the ground. As a racer moves stealthily through dense vegetation, its dull, uniform dorsal color blends well with the surface litter of dead plant material. In prowling, the snake glides along rapidly and alertly, in a jerky fashion, with frequent momentary pauses and changes of direction. Because of its inconspicuousness, it is not likely to be detected by the prey until it is close at hand. The snake is ready to dash in pursuit of any small animal that flies, jumps or runs to escape.

On August 27, 1955, my daughter observed a large racer hunting among tall weeds at the edge of the pond on the Reservation. Several times in the course of its movements, it flushed small frogs (_Rana pipiens_) and each time the snake darted in unsuccessful pursuit of the rapidly hopping frog. On several occasions I have been led to a blue racer by the distressed croaking of a frog that the snake had captured. In each instance, despite my cautious approach, the racer saw me before I detected it, and then darted away, abandoning its prey. On one occasion, while I was still a few yards from the racer, and before the latter had detected me, the frog broke free and hopped away rapidly through tall grass and weeds, and after several leaps, hid, concealed by dense screening vegetation. The racer darted in pursuit but could not find the frog. For several minutes the snake persisted in an active search; with forebody elevated and head held high, it would turn first in one direction and then in another, with nervous, jerky movements, obviously keyed up to a high pitch of excitement. Then it became aware of my presence, lowered its head, and glided away rapidly, abandoning the search.

Although the racer depends to a large extent on sight to find its prey, scent may play some part also, as indicated by the presence in the food of young mammals taken from nests, some probably found underground. Near Garnett, Kansas, on May 4, 1952, Richard B. Loomis found a racer attacking a collared lizard (_Crotaphytus collaris_) beneath a large flat rock. The lizard was retaliating by biting the snake's neck. The posterior part of the snake protruded into the open, and its thrashing had directed the attention of the observer to it. Whether the racer first found the lizard under the rock, or followed it there after flushing it in the open is unknown.

An encounter between a large blue racer and an adult Great Plains skink (_Eumeces obsoletus_) on August 30, 1948, was described as follows: "The skink, grasped by one flank, had twisted back and seized the skin of the snake's neck in a bulldog grip, and they lay interlocked, motionless except for their rapid panting, and occasional straining of the skink to bite harder or of the snake to shift its grip and work its jaws toward the skink's head. The racer broke the skink's grip, and began to swallow it head first. When only the hind legs and tail of the skink still protruded from the racer's mouth, I lunged forward in an attempt to catch both reptiles. With a sudden movement the snake disgorged the skink, which darted away into the grass and escaped" (Fitch, 1955:78).

_Composition of Food_

Many authors have contributed to knowledge of the racer's food habits. In most instances the records have been few or casual, but several intensive studies have been made, notably by Surface (1906) in Pennsylvania, Ortenburger (1928) for the species as a whole, Uhler, Cottam and Clark (1939) in Virginia, Clark (1949) in Louisiana, Auffenberg (1949) in southern Texas, Hamilton and Pollack (1956) in Georgia, and Klimstra (1959) in southern Illinois. However, the findings of different authors are not strictly comparable; some have made general statements concerning the food habits but have mentioned specific items only when these were considered unusual. Certain authors have listed individual prey animals eaten; others have indicated the percentages (in bulk or in frequency) that the different kinds of prey comprised. Some writers have identified food animals only in broad categories such as "insect," "beetle" or "snake" while others have undertaken specific determinations for all the prey or for certain taxonomic groupings that were subjects of special interest.