THE ROLE OF THE SENSES IN MARE-FOAL

Transcription

1 Applied Animal Ethology, 6 (1980) Elsevier Scientific Publishing Company, Amaterdam - Printed in The Netherlands THE ROLE OF THE SENSES IN MARE-FOAL RECOGNITION THOMAS R. WOLSKI, KATHERINE A. HOUPT and RUTH ARONSON Department of Physiology, Biochemistry and Pharmacology, New York State College of Veterinary Medicine, Cornell University, Ithaca, New York (U.S.A.) (Accepted for publication 20 April 1979) ABSTRACT Wolski, T.R., Houpt, K.A. and Aronson, R., The role of the sen8ee in mare-foal recognition. Appl. Anim. Ethol., 6: The relative roles of auditory, visual and olfactory cues in the mutual recognition of mares and their suckling foal8 were studied. Foals were tested for their ability to differentiate between their own mother and a similar lactating mare after cues emanating from the mares had been modified. Visual cues were either altered or eliminated, and olfactory cues altered : auditory cues were not modified, but the frequency of calls was measured during the various trials. Similar trials were conducted in which the ability of mares to differentiate between foals was examined. Both mares and foals were severely hindered in their attempts to locate one another when visual cues were eliminated and olfactory cues were modified; the effecta of either visual cue elimination or olfactory cue modification alone were similar, and neither one alone affected relocation attempts by either mares or foals to the same degree as the combination of both. Merely altering visual appearance did not affect the rate at which one partner identified the other. Play-back trials of the recorded neighs of foals and mares indicated that a mare shows some discrimination in foals calls by responding more often to the call of its own foal, but that a foal is not able to identify the neighs of its mother. During the relocation trials, however, both mares and foals non-selectively approached the most vocal of the test pair. A foal seemed to use the initial reaction of a mare to its approach aa a final acceptance cue. Snapping and clicking of the teeth by the foal while retracting the lips ( champing ) were observed as the foal approached or was approached by the mare, and these were interpreted aa being submissive gestures. Nickers were heard on the close approach of mare and foal, and mutual sniffing occurred; these behaviors appear to be the means of final identification between the pair. INTRODUCTION Domestic horses form a strong maternal bond with their foals. When separated, the mare can relocate the foal and the foal can relocate the mare. Alien foals are rejected by the mare. Olfactory, visual and auditory cues are all normally assumed to be used by a mare in recognition of her foal (Waring et al., 1975). Sheep and cattle husbandrymen routinely modify the odor of an orphan in cross-fostering attempts. Several techniques are used, the most

2 122 common is to apply fresh milk from the prospective mother to the skin of the orphan. Tyler (1972), in her study of the New Forest ponies, mentions the successful acceptance by a mare of an orphan foal after draping the foal with the skin of the mare s own recently killed foal. It seems unlikely the skin would present the mare with a normal visual picture of her foal; the odor of the skin was probably of primary importance. Alexander (1977) has recently reviewed the literature concerning ewe-lamb recognition and presented some new work on the subject. In these studies, the cues emanating from one or both partners were removed or altered and the response of one or both animals observed. Conclusions regarding the relative importance of visual, auditory and olfactory cues in ewe-lamb recognition differed according to the experimental methods employed, but in general these studies indicated that ewes use olfactory cues to identify their lambs at close range, but make use of visual and auditory cues at a distance. Young lambs use auditory cues to identify their mothers, while older lambs rely more on visual cues. Similar cue-modifying experiments have not been tried in studying the mare-foal relationship. This report represents a first experimental attempt to rank the importance of smell, vision and audition in mutual recognition by the foal and mare. Our approach has been to alter one or more cues from one member of the marefoal pair and observe the attempts by both at finding one another after a short separation. METHODS Six mares, three Thoroughbred, two Standardbred and one Quarterhorse, with their suckling foals (3 fillies, 3 colts) were used in Tests 1 and 2. In Test 3, fourteen mares (5 Thoroughbreds, 2 Standardbreds, 2 grade horses, 1 Quaterhorse and 4 Ponies) and their suckling foals were used. All foals were born at the Equine Research Park, Ithaca, N.Y., maintained by Cornell University. Foals and mares were housed in individual box stalls. Tests were conducted when the foals were between 2 weeks and 5 months old. Testing procedures (1) Alteration of visual cues only: open paddock test In this first procedure, two lactating mares were restrained 15 m apart in a large open paddock. One of these mares was the test foal s mother and referred to as mare below. The other was the mother of another test foal and was designated as alien mare. The mares were paired on color and marking similarities. The foal was left in a barn for a ten- to twenty-min separation period and the number of vocalizations it made during that time were recorded (pre-test vocalizations). After ten min, the foal was led out and released at a point approximately 15 m from each mare, and its attempts

3 at relocating its dam observed. Times of vocalizations by each of the three animals, times of approach (within 2 m of a mare) by the foal to either the mare (correct approach) or alien mare (error approach), and the total time needed by the foal to successfully locate its own mother (spend 15 s within 1 m of her) were recorded. Vocalizations during the 15-s period needed to confirm a successful approach were not used in any of the analyses below. A maximum of 5 min was allowed for each trial. This trial was repeated on a different day using the same three animals, except that the mares were visually disguised using colored horse blankets and padded traveling hoods (Fig. 1). Each foal was tested four times with undisguised (normal appearance) mares and four times with the disguised (altered appearance) mares. To test the mare s method of recognizing her foal, the above procedure was reversed; two foals, matched for size and color, were restrained in the paddock and the mare was kept indoors for lo-20 min. 123 Fig. 1. Appearance paddock test. of mare with blanket and traveling hood in place for the open (2) Elimination of visual cues and alteration of olfactory cues: stall test The same mares and foals were used. Pairing of the subjects and the pretest situation were identical to the above, with the exception that the pretest vocalizations were not recorded. The tests were conducted in a large paddock (90 m X 60 m) containing a 30 m X 4 m X 4 m covered shed at its

4 124 center. The shed was completely enclosed on three sides and divided into ten stalls, each stall being separated by solid planking and fronted by a door and solid planking to a height of 1.5 m. Two stalls 15 m apart, neither being an end stall, were enclosed completely from the top edge of the planking to the roof with burlap; these were designated as the closed stalls. Two stalls, one adjacent to each of the closed stalls, also 15 m apart and neither an end stall, were left unmodified and designated as the open stalls. All the trials in this procedure were completed in one week of intensive testing following the completion of the previously-described paddock tests. Two mares were restrained in the test stalls facing outward and the test foal was brought to the front of the stalls, positioned 20 m from each test stall, and allowed to find its mother. The foal was considered to have successfully located its mother when it spent 15 s within 2 m of its dam s stall. Five min was the maximum time for each trial. Four trial variations were conducted. For Trial 1, the two mares were restrained by an attendant in the open door of the open box stall (vision +, olfaction +). In Trial 2, the mares were placed unrestrained in the closed stalls with the attendant standing by the stall door (vision -, olfaction +); the attendant stood by the door as a control for the attendant who was present restraining the mare in the vision + trials. Before Trials 3 and 4, a mentholated ointment (Vi&s Vapo-rub) was applied about both the foals and mares nostrils and faces, and the Trials were conducted in the open and closed box stalls as for Trials 1 and 2 (Trial 3: vision +, olfaction -; Trial 4: vision -, olfaction -). The mentholated ointment was chosen because of its pungent odor, ease of application, and length of action. We felt the animals, and especially the foals, would not tolerate face masks and nose plugs as used by others on stallions (Wierzbowski, 1959). Neither mares nor foals appeared agitated by the ointment after application. Since the test situation limited the animals to face-to-face approaches, the mentholated ointment about the face made the odor emanating from this area more nearly identical in each test animal; the ointment also probably altered the olfactory input to each animal to some degree, although this was not measured. As with the previous procedure, no attempt was made to modify vocal exchanges. The sequence and time of all neighs were recorded. Approaches by the foal to each mare s stall and total time for locating its mother were recorded. Instances of occurence of the facial expression of juvenile horses submissive champing or Unterlegenheitsgebaerde (Zeeb, 1969) were recorded. This entire procedure was reversed to test the mare s ability to locate her foal. Foals were matched in size and color. (3) Voice recognition by mares and foals: playback tests A tape recorder (Uher 4000) was used to record neighs of each mare and of each foal. The mares and foals were separated and several neighs of each individual animal were recorded. One loud neigh was selected for use in the experiments. In order to investigate the responses of the horses to the re-

5 corded voices, a loudspeaker was placed out of sight of the horses in each of two adjacent box stalls with the doors closed, in a paddock free of other horses. Each horse was held 3 m from both loudspeakers. One loudspeaker was used to broadcast one horse s neigh and the other the second horse s neigh. When a mare was tested, one voice was that of her foal and the other that of an alien foal. When a foal was tested, one voice was that of its mother and the other that of an alien mare. Horse neighs were paired with horse neighs and pony neighs with pony neighs. A total of six neighs were played to each animal, 3 neighs of its own mother or foal and 3 of an alien. The time between neighs was at least 20 s, or until the test animal had ceased responding to the previous recording. A neigh beginning within 10 s of the end of a broadcast was considered a response. Statistical methods Non-parametric procedures are used throughout. The Mann-Whitney and sign tests of significance and the Spearman rank coefficient (r8) are described by Conover (1971). 125 RESULTS (1) Alteration of visual cues: open paddock test (a) Foal locating mare. Altering the appearance of the mare had no effect on the mean success times of the foals. The mean time for the foal to locate its mother when she was disguised was actually less (i = 89.0 s) than when she was not disguised (X = s); these differences are not significant (Mann- Whitney test, DO.05) (Table I). The success times of the six foals improved to some degree over the four trials. The only significant change, however, TABLE I Times foais took to locate mare in open paddock test; mean pre-test vocalization rate by the foal Foal Mean time to locate mare (s) Mean pre-test Mare unaltered Mare disguised vocalizations/l0 min 34 (Female) (Male) (Male) (Female) (Female) (Male) i=

6 126 came between the s mean trial time in the first set of trials and the 85.3 s of the next set (third trial set mean = 67.3 s; fourth trial set mean = 48.9 s). In addition, no overall age-uccess time correlation could be found (rs = -0.24). Thus, the foals seemed not to improve in this task beyond the improvement associated with becoming familiar with the test procedure. The paradoxical lower scores noted in the series of disguised trials when compared with the undisguised trials apparently results from this effect. Most foals were initially tested with the mares undisguised. Eliminating this first score from the undisguised trials produces a mean absolutely, but not significantly lower than the disguised trials (X [undisguised] = 73.7 s, X [disguised] = 89.0 s; Mann-Whitney test, E-0.05). Because no statistically significant differences between the results of either group were found, all 48 trials are combined in the calculations below. Pre-test vocalizations recorded for all the foals during the separation period were highly variable, with means ranging from 13.1 to 44.3 per 10 min (3c = 28.5) (Table I). Calls were loud neighs in response not only to the calls of the mare from the paddock outside, but also to those of any other horses, including a stallion. It was impossible to record to which loud vocalization the foal was responding, as several horses often called simultaneously. It did appear, however, that the foal was answering any loud vocalization. Correlation between pretest vocalizations and success times was low (r, = 0.41). Vocalizations during the actual test period were primarily loud neighs. Nickers, an equine vocalization described as a low frequency, audibly pulsated, low amplitude sound (Waring et al., 1975), were heard when the mares and foals were in close proximity. All vocalizations were recorded, but since we are not certain we heard all, or even most, nickers the tabulations below include loud neighs only. Vocalization rates of all test animals in those trials ending in a foal s successful location of its mother within 60 s (rapid) were compared with those trials which lasted over 60 s (slow) (Fig. 2). There were dramatic and significant differences between the rates of vocalizations of the mares and alien mares in the more successful trials; 8.0 neighs/min for the mares, compared with 1.3 neighs/min for the alien mares (Mann-Whitney test, P<O.OOl). Also, in the more rapid trials, the rate of mare vocalizations (8.0 neighs/min) was significantly higher than the rate of 1.4 neighs/min for the same animals in the less successful trials (Mann-Whitney test, P<O.OOl). The foal calling rate seemed to match very closely the rate of calling of the most vocal individual, the mare in this case; a pattern repeated in the other test situations. Over the course of all the successful trials, the rates of calling were higher during the first half of the trials than during the second half for each of the test animals (sign test, X0.05 for each (Table II). These calculations do not include vocalizations heard in the 15 s after a correct approach if that approach terminated the trial.

7 ? *=6.0- c Lo- : :4.0- a!3.0- N = f I.o - L dr than 60 rrcondr Fig. 2. Foal locating mare. Open paddock test. Mean vocalization rates for the three test animals comparing rapid trials with slow trials. Rates are averaged for all animals in each class. TABLE II Comparison of the rates of calling by the test animals in the fit trial with the second half of each successful trial half of each successful Test animal Difference of mean vocalization rates (first half-second half) (neighslmin) Paddock tests Foal locating mare Mare Alien mare Foal P<O.O5 P<O.O5 P< 0.05 Mare locating foal Foal Alien foal Mare PBO.05 P>O.O5 P>O.O5 Stall tests Foal locating mare Mare locating foal Mare Alien mare Foal Foal Alien foal Mare P>O.O5 P> 0.05 PBO.05 P>O.O5 P>

8 128 (b) Mare locating foal. The mares performed appreciably better than their offspring in these trials, but, as was the case with their foals, failed to show any difficulty in identifying their visually altered partner. The mean time in the undisguised series of trials was 31.7 s, and in the disguised trials 37.4 s (Mann-Whitney test, DO.05) (Table III). Analysis of vocalizations during the trials in which the mare located its foal within 30 s (rapid) and those in which the mare needed more than 30 s or was unsuccessful (slow) did not reveal significant differences between the rates of vocalization of any of the three test animals (Fig. 3). As in the previous trial sequence, however, both natural partners are more vocal in the rapid trials than in the slow trials. A comparison of the vocalization rates of the foal, alien foal and mare showed only slight and insignificant differences between the vocalization rates of the first half of the trials and the second half for either the foal, alien foal or mare (sign test, BO.05 for each) (Table II). Vocalizations during the 15-s end-point determination period following a correct approach are not included in these tabulations. Pretest vocalizations by the mares showed no correlation with success time in locating the foal (range of means = per 10 min, Table III) (rs = 0.03). As with the foals in the previous procedure, the neighs of the mares seemed a response to any loud vocalization by any other horse in the barn or outlying paddocks ?.E t6.0 - r,;s.o - 5 f4.0- a E :2.0- s I.0 - Trials lasting lrsr Trlals lortingmorr than 30 second8 thon 30 mcondr Fig. 3. Mare locating foal. Open paddock test. Mean vocalization rates for the three test animals comparing rapid trials with slow trials. Rates are averaged for all animals in each class.

9 129 TABLE III Times mares took to locate foals in open paddock test; mean pre-test vocalizations by the mare Mare Mean time to locate foal (s) Foal unaltered Foal disguised Mean pre-test vocalizations/l0 min f= (2) Alteration and elimination of visual and olfactory cues: stall test (a) Foal locating mare. Both visual and olfactory cue alterations hindered the attempts of the foal to locate and identify its mother (Fig. 4). Mean times of each of the first three trial categories (vision +, olfaction + = 22.3 s; vision -, olfaction + = 61.3 s; vision +, olfaction - = 91.7 s) were significantly lower 200 t - b 3 Zl60- i3 pa 0.05 El60- x ;,140- ki 0 -,120- = c g 100 a :! kl 0 20 VISION+ mi VISIO GS OLFAC* LFAd OLFA LFA Fig. 4. Foal locating mare. Box stall test. Mean trial durations for four trial categories.

10 130 than the fourth (vision -, olfaction - = s) (Mann-Whitney test, KO.05). Neither an age-success time correlation nor any improvement over the course of the trials could be demonstrated in the success time data; in fact, some of the older foals in the group did much more poorly than the younger ones. Vocalizations recorded were again loud neighs; nickers were heard when the foal was reunited with its mother. During the vision deprived (vision -) tests, a much higher level of vocal activity compared with the visually unaltered trials (vision +) was apparent. A tabulation of the mean rates of vocalization during these tests indicated this was due to difference in calling by the alien mares in these trials (Table IV). They called a mean of 0.5 times/min when they were able to see the searching foals, but called at a rate of 3.5 times/min when they could not (Mann-Whitney test, P<O.O5). This latter rate approximated that of the mare which gave 4.0 neighs/min during vision - trials; the mares, however, called at a nearly identical rate (3.7 neighs/min) during vision + trials. Differences in the rates of calling by the mares were also evident and significant in comparing trials lasting less than 60 s with those taking longer than 60 s (Table V). In the former, the alien mare is much less vocal than the mare (1.3 neighs/min compared to 5.2 neighs/min; Mann-Whitney test, KO.05); in the latter, the calling activity of the two is nearly identical (2.8 and 2.5 neighs/min). As with the previous tests, these figures do not include the 15 s following a correct approach used to determine a trial end-point. Total vocal activity for each of the test animals, the mare, alien mare and foal, was only slightly different in each half of the successful trials, and none of the differences are significant (sign test, DO.05 for each) (Table II). Calling did not occur at a uniform rate over the entire trial, however. The differences in calling rates noted above were still evident even if a shorter time period before approaches was examined. Foals were more likely to make a successful approach following a peak of TABLE IV Mean vocalization rates during stall tests (foal locating mare); vision + compared with vision - trials, and olfaction + compared with olfaction - trials Mean vocalization rates (neighs/min) Mare Alien mare Foal Vision + Vision * b Olfaction + Olfaction a*b P<O.O5.

11 131 TABLE V Mean vocalization rates during stall test (foal locating mare); rapid trials compared with slow trials Mean vocalization rates (neighslmin) Foal Alien foal Mare Trial end point < 60 s Trial end point >60 s aqb P-CO b calling activity by the mare, and an incorrect approach following a burst of increased calling by the alien mare. Neighing by the dam was higher in the 30-s period before the foal made a correct approach to the mare (5.1 neighs min) than before an error approach to the alien mare (2.5 neighs/min) (Mann-Whitney test, P<O.Ol) (Fig. 5). Also, the mare was the more vocal animal before a correct approach (mare rate = 5.2 neighs/min, alien mare rate = 3.1 neighs/min) and the alien mare was more vocal before an error ap preach (alien mare rate = 3.3 neighs/min, mare rate = 2.0 neighs/min) although these differences are not statistically significant. Unsuccessful trials were terminated after 5 min. Figure 5 indicates that vocal activity of both mare and alien mare remained high even at the end of 6.0 P t Foal succorsfully locnfing mar0 Approach loon alien Torminofion of man by foal unsuccrrrful rrarch for more by fool Fig. 5. Foal locating mare. Box stall test. Vocalization rates during the last 30 s of a trial before the successful location of the dam by the foal, before an error approach by the foal to the alien mare, and during the last 30 s of an unsuccessful trial.

12 132 this period. By this time, however, there was no vocal activity from the foal. This was also associated with little or no motor activity. Eight times in the 12 vision + trials (once in each of 6 trials, twice in 1 trial) a foal approached a mare while clicking its teeth and retracting its lips ( champing ). In 6 instances this was seen before a final approach by a foal to the mare, and twice a foal exhibited this behavior while approaching an alien mare. All foals except one male showed this behavior at least once. Champing was not seen in any of the vision - trials. Nickers were heard when the mare and foal were in close proximity. Foal approaches to an alien mare were greeted by aggressive threats; the mare extended her head toward the foal and pulled her ears back. Mutual sniffing and relative immobility of the foal were seen following a correct approach by the foal pl60- z?60- Z z glsob a 5 I20- t I- gloo- I so- - p SO.01 - b a trl OLEAC+ OLmC+ OLFAC- OLFAC- Fig. 6. Mare locating foal. Box stall test. Mean trial durations for four trial categories. (b) Mare locating foal. The performance of mares was more affected by sensory alteration than that of their foals when either visual or olfactory cues alone were modified (Fig. 6). The mares took over twice as long to locate their partner as did the foal when vision was eliminated (vision -, olfaction +; mean success time, mare = s, foal = 61.3 s), but only somewhat longer when olfaction alone was modified (vision +, olfaction -; mean success time, mare = s, foal = 91.7 s). Thus, alteration of either sensory modality affected performance of the mares to a similar extent. A

13 significant difference in the success times of the mares in the four trials was demonstrated between the vision +, olfaction +, (19.2 s) and vision -, olfaction -, (194.0 s) trials (Mann-Whitney test, PCO.01). The vocalization rates of the three test animals were analyzed (Table VI). The foal was significantly more (Mann-Whitney test, P<O.O5), and the alien foal significantly less (X0.01), vocal in the shorter trials when compared with their respective mean rates in the trials lasting more than 60 s. The rate of calling by the mare closely approximated the rate of calling by the most vocal foal in both categories. Vocal activity in each half of the successful trials was again very similar for each of the test animals (sign test, DO.05) (Table II). During the 30-s period prior to a successful location of the foal by the mare (not including the final 15 s end-point determination period), the foal was much more vocal (2.2 neighs/min) than during the same period prior to an approach by the mare to an alien foal (0.50 neighs/min) (Mann-Whitney test, RO.001) (Fig. 7). Before an error approach by the mare, both foals were similarly quiet (foal rate = 0.5 neighs/min, alien foal rate = 0.7 neighs/min); but, prior to a correct approach by the mare, the foal was much more vocal than the alien foal (foal rate = 2.2 neighs/min, alien foal rate = 0.7 neighslmin) (Mann- Whitney test, P<O.O5). The same previously-noted calling pattern is seen in that the mare neighed in response to the most vocal foal; the rate of calling approximated that of the foal before the correct approaches and the alien foal in the error approaches. Three instances of champing by a foal were observed in the 12 vision + trials, 2 of these at an error approach by the mare. No occurences were noted in the vision - trials. The behavior was again seen in both sexes (2 females, 1 male). Most mares, on approaching an alien foal s stall, sniffed briefly and left quickly. A foal was restless to extremely agitated at the approach of an alien mare, but quiet and immobile when approached by its dam. Nickers were sometimes heard during this approach. A correct approach was followed by mutual sniffing. 133 TABLE VI Mean vocalization rates during stall tests (mare locating foal); rapid trials compared with slow trials Mean vocalization rates (neighs/min) Foal Alien foal Mare Trial end point < 60 s Trial end point > 60 s b 1.5d 2.0 kb P<0.05;C*d PCO.01.

14 Mare ruccossfully locating foal Approach to on olirn Termination of foal by marr unsuccrssful soarch for fool by mare Fig. 7. Mare locating foal. Box stall test. Vocalization rates during the last 30 s of a trial before the successful location of the foal by the mare, before an error approach by the mare to the alien foal, and during the last 30 s of an unsuccessful trial. (3) Voice recognition by mares and foals: playback test All of the horses were attentive to the recorded voices. They pricked up their ears and oriented towards the stall which held the loudspeaker as the neighs were played. Mares neighed more often in response to hearing their own foal s voice than in response to hearing another foal s voice, but the difference was not statistically significant (sign test, BO.05). The mean number of responses of the mares was neighs in response to their own foal s voice and 1.8 i 0.2 neighs in response to an alien foal s voice when presented with a sequence of 6 calls, 3 in each category. The foals neighed a mean of 1.7 f 0.4 times in response to their mother s voice and 1.3 f 0.5 times in response to the other mare s voice (sign test, BO.05). DISCUSSION Vocal cues appear to be of primary importance when members of a marefoal pair are attempting to locate one another. Although mares showed some evidence, baaed on response to recorded neighs, of recognizing their foal s voice both mares and foals responded to and approached the animal which vocalized more often than the other in our test situations. In almost all of the present experiments, the test animal initially approached the most vocal choice, not necessarily its natural partner. Vocal responses in the searching animal were matched most closely in rate to that of the most vocal of the restrained animals in both test series, again not necessarily its natural partner. In both the paddock and stall tests, whether the foal was locating the mare, or the mare searching for the foal, the rates of vocalization for each half of the successful trials were either the same, or they were higher in the

15 first half of the trial. Bursts of calling activity at any particular point in the trials, for example either at the startor nearthe end of a successful trial, were not consistently noted by the observers, although calls were sometimes clumped. Analysis using the stall test data of the 30-s period prior to successful or error approaches indicates that the differences in calling rates of the test animals not only existed over the entire course of the trials, but existed at several points during the trials as well. It may be concluded then that the animals are not calling because they recognize one another, but rather find one another because they are calling. This conclusion is supported by the high rates of vocalization during the pre-test period. In all cases the more rapidly concluded trials were associated with overall higher rates of calling by the natural partner of the searching animal. Correct approaches were more often made following at least a 30-s period in which the natural partner s calling rate was higher than the alien test animal s, and an error approach after at least a 30-s period in which the alien test animal s calling rate was the higher. The vocalization rate of the alien mare in the stall test series pointed to visual recognition even at a distance. In the closed stall trials the rate of calling by the alien mare was approximately that of the mare. In the open stall trials, however, the mare s vocalizations rate was about the same as in the closed series, but the rate of calling by the alien mare was quite low. Overt olfactory behaviors were noted only when the mare and foal were in close proximity. Since the observed low rate of calling by the alien mare was fairly constant over these trials, we assume that she recognized at the initiation of the trial, when the foal was usually between 10 and 20 m from each box stall, that the foal was not her own. This identification we feel prompted the lower rate of calling in these trials. Upon approaching within several meters of a restrained mare which it could see, the foal sometimes stopped, held its ears facing forward or outward, and often retracted its lips and snapped and clicked its teeth. These latter behaviors were occasionally seen in the restrained foal when approached by a mare it could see. We interpreted these as submissive gestures, and propose to call the grinning-teeth clicking combination champing (Fig. 8). In contrast to Feist and McCullough s (1976) findings that among wild horses only colts (male foals) showed this champing, both colts and fillies (female foals) in this study, and that of Williams (1974), champed when approaching or being approached by mares. Mares almost always threatened an alien foal whether they approached the foal or were approached by it; the threats were usually mild, but several times mares kicked at alien foals. Lack of threat behaviors probably initiated closer approach by a foal. During an approach of the mare and foal, soft neighs were heard from one or both partners. The mare would then smell around the foal s head. This is the first point at which we could identify overt olfactory behavior. In each variation of the stall tests, both mare and foal had a marked difficulty in locating their partner when we modified the olfactory information they were transmitting and receiving. This result, and the consistency of the ap- 135

16 136 Fig. 8. Submissive champing by a foal upon being reunited with ita dam during the stall test. pearance of olfactory behavior at this point in the trials, leads us to conclude that olfactory cues are important in close range, final identification after separation. The flehmen response was never observed in either mares or foals. The postural changes and motor patterns described above were commonly seen and may have been the cause of the failure of visual disguises to hinder location attempts in the paddock test. The test animals usually quickly approach one of the restrained animals in the paddock tests; in contrast to the vision - stall tests, the restrained mare or foal, even with the traveling hood and blanket in place, retained a horse-like appearance. A disguised animal would still be able to visually identify the searching animal as its partner. The lack of aggression in the disguised mare would prompt closer inspection by the foal; the immobility and ear positions of a disguised foal would allow the mare to investigate more closely and make olfactory identification as suggested above. It is not surprising that both mares and foals did so poorly in the vision -, olfaction -, stall tests. Here we eliminated long range visual identification, the presence of a horse-like figure with which to associate the loud calls of the hidden partner, and the possibility of transmitting close range postural signals, and we masked olfactory cues which apparently are important in close-range identification.

17 137 More study of the vocal specificity of the nicker needs to be done. Tyler (1972) feels that foals over several weeks of age could recognize their own mare s nickers, and presumably the foal s nickers are likewise individually recognized by the mare. We found some indication that foal neighs could be recognized individually by mares in the playback tests, but the other tests conducted indicated that the neigh is a non-specific alerting cue. Visual identification of the foal by the mare seems rapid, even at a distance. In range or pasture situations, a mare maintains fairly strict visual contact with her foal for at least 6 months after birth (Tyler, 1972; Feist and McCullough, 1976). Since most horse bands are small (under 20 animals), a mare might only need to lift her head to see whether or not to be concerned with a distress call from a foal. We are unable to explain the differences between the performance of mares and foals in the stall tests. When either vision or olfaction alone was modified, the mares were less efficient than the foals in locating their partners even though the success times of both mares and foals were nearly identical when cues were unmodified, or when both visual and olfactory cues were concurrently modified. In the paddock tests the mares were easily able to locate and identify their foals; the mean success time of the mares was less than half that of the foals. It would seem reasonable to expect this differential, presumably the result of either more sensory experience, greater sensory development or adaptability to the test situation, to persist in the success times of the stall tests. If, perhaps, the mare was more agitated than the foal and less able to attend to the test problem, all four variations of the stall tests would be expected to have elevated success times, rather than only the two with one cue modified as we found. CONCLUSION Mare-foal recognition depends on visual, auditory and olfactory cues. Mares, at least, are able to recognize their foals at a distance of ten meters or more, and both mares and foals communicate recognition at short distances with a series of postures and motor patterns including threats, immobility or flight, and a specific submissive signal of the foal, champing. Loud calls, neighs, do not seem to be recognized specifically by either mare or foal; more study of the signal specificity of the nicker is needed, although the observation of its appearance during the final stages of the reunion of mare and foal in these studies does not disagree with Tyler s (1972) claim that nickers are individually recognized. Olfactory behaviors were noted only when the mare and foal were in close proximity; the delays in location caused by masking olfactory cues imply they are important in mare-foal recognition. Further studies of the relative roles of these sensory modalities in the mare-foal relationship are needed. Because of the design and goals of our studies, many of the observations of the close proximity behavioral interactions were more qualitative than quantitative. We hope our experiments prompt further inquiry into these and other aspects of the problem.

18 ACKNOWLEDGEMENTS This study was supported by a grant from the Morris Animal Foundation. We wish to thank our many volunteers especially Betty Kramek, Peter Davis, Paul Shepherd, Bill Lombard and Rob McCall. REFERENCES Alexander, G., Role of auditory and visual cues in mutual recognition between ewes and lambs in Merino sheep. Appl. Anim. Ethol., 3: Conover, W.J., Practical Nonparametric Statistics. Wiley, New York, pp. 121, 224, 245. Feist, J.D. and McCullough, D.R., Behavior patterna and communication in feral horses. Z. Tierpsychol., 41: Tyler, S.J., The behavior and social organization of the New Forest ponies. Anim. Behav. Monogr., 5: Waring, G.H., Wienboweki, S. and Hafez, E.S.E., The behavior of homes. In: E.S.E, Hafez (Editor), The Behaviour of Domestic Animals. 3rd edn, Williams and Wilkins, Baltimore, pp Wierzbowski, S., The sexual reflexes of stallions. Roczn. Nauk Roln., 73-B-4, pp Cited in: E.S.E. Hafez (Editor), The Behaviour of Domestic Animals. 3rd edn, Williams and Wilkins, Baltimore, 1975, p Williams, M., The effect of artificial rearing on the social behaviour of foals. Equine Vet. J., 6: Zeeb, K., Die Unterlegenheitsgebffrde des noch nicht ausgewachsen Pferdes (Equus caballus). Z. Tierpsychol., 16: