Abstract: Observations of sociosexual behavior of adult ponies, made on two harem groups (each comprised of one vasectomized male and three females), were correlated with follicular development and ovulation for a total of 15 cycles (minimum of 2 cycles per female). Mean cycle length (interovulatory interval) was found to be 19.7 days, with behavioral estrus lasting 7-8 days (5.5 days preovulatory; 2.3 days postovulatory). Estrous females typically showed increased frequencies of approaching and following the stallion, urinating, presenting, clitoral winking, and tail raising. Approaching and following the stallion appeared earlier and persisted longer than other estrous responses. Deviations from the modal estrous pattern included cycles with subestrus, continual estrus, behavioral estrus in the absence of ovulation, and displays of female mounting. Dominance tests revealed that a mare's status was unaffected by the phases of the estrous cycle. The presence of more than one estrous female affected the copulatory performance of both stallions, most notably in reduced latencies to first mount, intromission, and ejaculation, in spite of differences between the stallions in sexual vigor. Each stallion usually selected the dominant mare for copulation when there were multiple estrous females present, but mounts were not displayed exclusively to one female per test. The social testing situation made apparent the importance of use of space in sociosexual communication in this species, particularly in avoidance of the stallion by diestrous mares and standing alone or in proximity to him by estrous mares.

Abstract: This paper presents a simple and widely applicable multiple test procedure of the sequentially rejective type, i.e. hypotheses are rejected one at a time until no further rejections can be done. It is shown that the test has a prescribed level of significance protection against error of the first kind for any combination of true hypotheses. The power properties of the test and a number of possible applications are also discussed.

Abstract: Twenty-six yearling horses were tested on a serial reversal learning discrimination combining spatial and brightness cues. An original discrimination of rewarded or nonrewarded stimuli was made followed by 20 daily reversals for position/brightness discrimination. Learning criteria were defined as 11 out of 12 correct, with the last eight responses all correct. Each horse was allowed 30 trials per discrimination to achieve criteria. Mean errors (ME) and mean trials (MT) required to achieve criteria were computed for each horse. A relative learning ability index (LAI) was calculated by the formula 1000/MT/ME. A daily emotionality score, based on a scale of one (tranquil) to six (very excitable) was assigned each horse each day after testing and a mean computed for each horse. A single subjective trainability score, based on a scale of one (difficult to train) to six (easy to train) was obtained for each horse from an independent trainer. Linear regression analyses for all 26 horses revealed a reduction in MT and ME (P<.01) over the 21-day test period indicating evidence of learning to learn. Differences (P<.05) were evident between sexes for MT and ME. Significant correlations between trainability scores and learning ability indices MT, ME, and LAI were evident for colts and geldings but not for fillies. Pooled data showed significant correlations between ME and trainability. There was a negative correlation (P<.05) between emotionality and trainability scores for all 26 horses, although the filly group did not exhibit significant correlation between these parameters.

Abstract: The development of litter and individual differences in the rate of ultrasonic signaling of neonatal rats was studied. Systematic variations among litters and individuals emerged, without differential treatment. These differences were not correlated with variations in general development as indexed by body weight. Two experiments using a cross-fostering design showed that litter differences developed independently of variations in postnatal environment. These results indicate that the variations among litters in ultrasound rate have a prenatal, possibly genetic, etiology and may represent reliable indicants of response to environmental stress.