Applied Animal Ethology, 6 (1980) 121-138 121 0 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 14853 (U.S.A.) (Accepted for publication 20 April 1979) ABSTRACT Wolski, T.R., Houpt, K.A. and Aronson, R., 1980. The role of the sen8ee in mare-foal recognition. Appl. Anim. Ethol., 6: 121-138. 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 exam- ined. 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 com- bination 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 in- dicated 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 sepa- rated, 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 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 pre- sented 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 ac- cording 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 study- ing 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 mare- foal 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 re- ferred 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 123 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 appear- ance) 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. Fig. 1. Appearance of mare with blanket and traveling hood in place for the open paddock test. (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 pre- test situation were identical to the above, with the exception that the pre- test 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 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 suc- cessfully 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 menthol- ated 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 (Wierz- bowski, 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 ema- nating from this area more nearly identical in each test animal; the ointment also probably altered the olfactory input to each animal to some degree, al- though this was not measured.