The ability to predict the effects that new or modified roads will have on species or populations of conservation interest Is critically important to protection efforts. We documented patterns of movement and spatial dispersion of two sympatric snake populations by radiotracking 34 Eastern Massasaugas (Sistrurus catenatus) and 13 Eastern Hog-Nosed Snakes (Heterodon platirhinos) over four years. The two species differed substantially in their movements (frequency, rate, tortuosity, distance) and ensuing spatial dispersion. Regardless of species, males were more vagile than female conspecifics during the mating season. The primary factors hypothesized to have generated the interspecific differences in movement and spatial dispersion were foraging mode, mating system, and reproductive mode. By combining our understanding of how these snakes used space with knowledge of their natural history and ecology, we examined which attributes of their spatial ecology might render S. catenatus and H. platirhinos most susceptible to road effects. For S. catenatus, our observations suggest that spatial fidelity and space use relative to hibernacula are the primary factors influencing the species' susceptibility to road effects. For H. platirhinos, tortuous and extensive movements, space use relative to hibernacula, and large spatial dispersion distances from hibernacula are likely the most important factors.

Although females of oviparous snake species presumably would benefit by modifying their thermoregulatory behavior while gravid, few studies have investigated whether gravid females actually thermoregulate differently than nongravid conspecifics in the field. To this end, we recorded body temperatures (T(b)s) from female Eastern Foxsnakes (Elaphe gloydi) housed in a large seminatural enclosure using temperature-sensitive radio-transmitters. Contrary to our expectations, gravid females did not maintain higher or less variable T(b)s than nongravid females. We suspect that the thermal environment available to gravid females at our site may render further increases in thermoregulatory effort, beyond that of nongravid females, unnecessary and potentially detrimental, given possible costs of thermoregulation.

Willson and Wilkie (1993) developed a novel procedure for assessing pigeons’ memory for the spatial location of food. Only one of four locations (consisting of an illuminated pecking key and grain feeder) provided food each day. Over days, different locations provided food. The pigeons’ tendency to revisit the location that was profitable on the previous day demonstrated memory for food-spatiallocation associations over a period of 24 h, retention longer than previously reported for this species. This basic finding was replicated and extended in three experiments. Experiment 1 demonstrated that location-food discriminations were also remembered well when established with successive rather than concurrent procedures. Experiment 2 demonstrated that pigeons can remember two location-food associations over 24 h. Experiment 3 showed that the discrimination training inherent in this paradigm is important for retention; retention was impaired when only the rewarded location was presented. Overall, this research suggests that cross-species differences in spatial memory performance may be due to quantitative rather than qualitative differences in the memory system underlying performance.

Six pigeons were tested on a one-trial-per-day variant of delayed matching of key location. In one condition, a trial began with the illumination of a pair of quasi-randomly selected pecking keys in a large 10-key test box. Pigeons' pecks to one key (the sample) were reinforced with 8-second access to grain on a variable-interval 30-second schedule, whereas pecks to the other key (the distractor) had no scheduled consequences. In the second condition, the nonreinforced distractor was not presented. In both conditions, subjects were removed from the apparatus after 15 minutes and placed in a holding cage. Subjects were subsequently replaced in the box after a delay (retention interval) of 30 seconds and were reexposed to the illuminated sample and distractor keys for 1 minute. If a pigeon made more pecks to the sample during this interval, the distractor was extinguished and subsequent pecks to the sample were reinforced on the previous schedule for an additional 15 minutes. If, however, a pigeon made more pecks to the distractor, both keys were extinguished and the subject was returned to its home cage. For all subjects, matching-to-sample accuracy was higher in the first condition. In a second experiment, the retention interval was increased to 5, 15, and 30 minutes, and then to 1, 2, 4, 8, 12, and 24 hours. Most subjects remembered the correct key location for up to 4 hours, and in one case, up to 24 hours, demonstrating a spatial-memory proficiency far better than previously reported in this species on delayed matching tasks. The results are discussed in terms of the commonly held distinction between working and reference memory.

A discriminal distance analysis procedure similar to that used by Roitblat (1980) was employed to test the hypotheses that animals either retrospectively (Spetch & Wilkie, 1983) or prospectively (Kraemer, Mazmanian, & Roberts, 1985) encode durations of events. Pigeons were required to discriminate 2-, 8-, and 10-sec presentations of light. Choices of red, orange, and green keys were correct after 2, 8, and 10 sec, respectively. The key elements in this design were (1) that some samples (8 and 10 sec) and some choice stimuli (red and orange) were more difficult to discriminate than were others, and (2) that an easy sample discrimination (2 vs. 8 sec) was mapped onto a difficult choice discrimination (red vs. orange), and vice versa. An examination of raw error scores and calculated confusion indexes in three experiments supported the hypothesis that subjects retrospectively, rather than prospectively, encode event duration.

Pigeons received training sessions in which a 3 x3 matrix of pecking keys was lit with red light. Pecking a particular key (but not the other eight keys) produced grain reward on an intermittent schedule. After this key-location discrimination was learned, subjects received occasional, non-rewarded test sessions, followed immediately by a “relearning” session. The time between these test sessions, which comprised a reference memory retention interval, varied from 1 to 30 days. No significant forgetting was found, even at the longest retention interval. This finding stands in marked contrast to typical results for pigeons tested on spatial working memory tasks (such as delayed matching to sample) in which forgetting is rapid. Our findings are consistent with Bond, Cook, and Lamb’s (1981) suggestion that the pigeon’s foraging ecology has favored the development of proficient reference rather than working memory.

Four pigeons previously trained to home to the roof of the University of British Columbia psychology building and 4 nonhoming pigeons were trained to discriminate between two sets of color slides projected onto a pecking panel of a Skinner box. One slide set consisted of photographs taken in the vicinity of the psychology building; the other set consisted of similar views taken at locations not previously visited by the homing subjects. All subjects were rewarded for pecking during slides from the first but not the second set. Every few sessions, new “Home” and “Away” slides were introduced during transfer tests. In a final transfer test, a completely new tray of Home and Away slides was introduced. The homing pigeons were slightly (but not statistically significantly) better at discriminating Home from Away slides. The implications of these results for understanding pigeons’ homing behavior, concept attainment, and spatial memory are discussed.