Snapping by Foals of Equus caballus

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Sonderdruck aus "Zeitschrift fiir Tierpsychologie"[2. Tierpsychol., 69, 42-54, 1985]

Alle Rechte, auch die des auszugsweisen Nachdruckes, der phoromechanischen Wiedergabe und der Obersetzun[vorbehalten.

Verlag Paul Parey, Berlin und Hamburg

New Yark State Callege af Veterinary Medicine, Carnell University, Ithaca

Snapping by Foals of Equus caballus

By S. L. CROWELL-DAVIS, K. A. HOUPT and ]. S. BUR~HA~I

z. TierpsychoI., 69, 42-54 (1985)@ 1985 Verlag Paul Parey, Berlin und HamburgISSN 0044-3573 / InterCode: ZETIAG

Neu: York State College of Veterinary Medicine, Cornell University, Ithaca

Snapping by Foals of Equus caballus

By S. L. CROWELL-DAVIS, K. A. HOUPT and ]. s. BURNHA:\I

With 3 figures

Received: August 30, 1984

Accepted: December 11, 1984

Abstract and Summary

Foals were observed to snap to juvenile and adult ponies and. rarely, to other foals ina wide variety of circumstances. There was no difference in the rate of snapping by coltsand fillies. Colts snapped to a stallion more often than would be expected if they were"napping randomly to any adult; fillies snapped randomly to either sex. In (mean ±SE)

-21±5 % of the cases the Foal approached the pony to which it snapped. In 24 ±3 % of thecases the foal was approached by the pony to which it snapped" while in 54 ±6 % of thecases the two were in immediate proximity prior to the snapping. 1\'0 aggression was directed toward the foal in 62 ± 5 % of the cases. Aggression was directed toward the foal beforesnapping in 31 ±5 % of the cases and after initiation of snapping in 7 ±1% of the cases.Adults and foals also nosed each other before and after snapping. Mares sometimes responded to snapping by their own foal, usually by exhibiting aggression toward the pOl'!y towhich the foal had snapped. It was concluded that snapping may have multiple signal functions, depending on context and that it may be a displacement activity of foals and younghorses derived from nursing behavior.

Introduction

Snapping was first described by ZEEB (1959), who called it the "Unterlegenheitsgebarde" (submissive gesture) of growing horses. English terms forthe behavior have included snapping (TYLER 1972; WILLIA~IS 1974; WELLS andGOLDSCHMIDT-RoTHSCHILD 1979), teeth-clapping (FEIST 1971; FEIST and MeCULLOUGH 1976), tooth-clapping (BOYD 1980), and champing (STEBBINS 1974;WOLSKI et ala 1980; HOUPT and WOLSKI 1982).

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Snapping by Foals of Equus caballus 43

The behavior is characterized by:1. Retraction of the commissure of the lips with partial exposure of the

teeth.2. Rapid up and down movement of the mandible.3. Turning the pinna of the ears so that the concave surface IS directed

laterally and slightly ventrally.4. Flexion of the carpus.

Only 1. and 2. occur consistently.

The exact meaning of snapping, and the reason(s) for its occurrence arestill unclear. Initially, snapping was considered to be a submissive behavior(ZEEB 1959; FEIST 1971). However, snapping does not have the effect of inhibiting aggression by adults (TYLER 1972; BOYD 1980). Also, it may be directed away from a pony which is immediately behind a foal and is the only ponyin the foal's immediate vicinity. In such a situation it would be difficult forthe behavior to function as ~ signal of submission because of poor visibility(BOYD 1980). BoYD (1980) has suggested that snapping may have a calmingeffect on the snapper.

The rate and context of snapping by foals were studied in order toevaluate changes with age, sex differences, and to obtain a better understanding of the causes and functions of this behavior.

Methods

A 3-year study was carried out on the developmental behavior of foals during theirfirst 24 weeks of life and the behavior of mares with foals living on pasture. The subjectswere 12 adult pony females (mares) and their 21 foals, 13 females (fillies) and 8 males(colts). 'There were no twin births. Some of the mares produced foals during 2 or 3 of the3 years of the study. 'The subjects were maintained on pasture with other ponies usuallypresent, including stallions, geldings, juveniles, and mares without foals. Each mare and herfoal were observed weekly as the focal dyad of a series of focal samples which totalled 2 h(ALTMANN 1974). In 1979 the day was divided into 3 periods: dawn to 11.00 h, 11.00 h to16.00 h and 16.00 h to dark (Eastern Daylight Time). Each week, two 20-min samples weretaken on each pair at random times during each division of the day. In 1980 and 1981 theday was divided into 4 periods: 05.00 h to 09.00 h, 09.00 h to 13.00 h, 13.00 h to 17.00 hand 17.00 to 21.00 h (Eastern Daylight Time). Each week, two IS-min samples were takenon each pair at random times during each division of the day. Observations were madeuntil the foals were weaned at 19 to 24 weeks of age, except for one filly which could onlybe observed through the 7th week. If circumstances such as illness of a subject preventedcollection of a sample, all available data were used for analysis. A total of 807.33 h offocal sample observations were made.

Subjects were usually observed from a distance of 3 to 4 m but could be approachedmore closely when necessary because they were habituated to the presence of neutralobservers. Behaviors observed were initially recorded on a tape recorder and subsequentlytranscribed. Whenever snapping occurred, a record was made of events occurring during,immediately prior to, and immediately after the event. A foal was recorded as snappingto a specific pony if the former directed its head towards the latter while snapping. Sincethis particular orientation did not always occur, information regarding the nearness andspatial orientation of the foal with other ponies, movement towards, away from, or pasteach other, vocalizations, aggressive behavior, and social interactions such as nosing ormutual-grooming were recorded in the initial notes.

44 s. L. CROWELL-DAVIS, K. A. HOUPT and ]. S. BURNHAM

From the notes, anyone of the following set of criteria was used to define which ponythe foal had snapped to:

1. The foal points its head toward the pony.

2. The other pony approaches the foal, walks past it, noses it or exhibits aggressiontoward it immediately prior to the foal's snapping. Other ponies in the foal's immediate vicinity have not made such movements or exhibited aggression toward it. Thefoal mayor may not point its head toward the pony exhibiting aggression.

3. The herd is moving along a path. Another pon}r is very close behind the foal whenthe foal stops and snaps.

4. A given pony is the only one in the foal's immediate vicinity.

Sometimes there was no apparent basis for assuming that the foal was snapping toa given individual. Such incidents, as applicable, were excluded from the evaluations of afoal's likelihood of champing to a given age/sex class.

In order to evaluate whether foals snapped indiscriminately to all age/sex classes ordisproportionately to certain age/sex classes, it was necessary to calculate expected valuesfor snapping to each age/sex class under the assumption of indiscriminate snapping. Forexample, if there were 7 adults and 3 other foals in the pasture besides the subject and thesubject were snapping randomly to any age class, it would be expected that the foal wouldsnap to an adult 7 times out of every 10 snappings. For each foal, a weighted average wasdetermined over all sample sessions which compensated for variation in herd compositiondue to births, illness, deaths, and pasture rotations.

To evaluate changes with age, rates were determined for each foal over 4-week periods,i.e., birth to 4 weeks, 5 to 8 weeks, etc. Data were evaluated with the sign test, Z2 test andMann-Whitney test (D~'lEL 1978).

Results

A. Occurrence

Field descriptions totalled 484 snappings, including both records ofsnapping by focal sample foals or of other foals to the focal mares, and ad librecords, i.e., snappings which occurred between focal samples.

Snapping was observed in a wide variety of circumstances, summarizedas follows.1. When another pony approached, walked past, or nosed the foal (Fig. 1).2. Foal-initiated interaction. The foal might be standing or feeding beside

another pony and suddenly snap to it without anything noticeable to theobserver having occurred to trigger the snapping. Also, foals approachedother ponies and snapped to them.

3. Following aggression by another pony toward the foal. Not all occurrences of foal-directed aggression were followed by snapping.

4. During courtship and copulatory behavior of the foal's mother and thestallion.

5. During or immediately after aggressive interactions involving other poniesin the vicinity of the foal.

6. During movement. Sometimes when the ponies were walking in singlefile along a path and another pony was close behind a foal, the foalwould stop and snap.

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B. Age of Ponies to which Foals Snapped

Foals were observed to champ to other foals. However, this was rare.Expected values for snapping to adults or other foals were calculated for19 foals from 294 snappings which occurred during a foal's own focal samplewhen at least one other foal was present. Juveniles over one year of age wereconsidered to be adults for these calculations. If snapping were occurringrandomly to all ponies present in the pasture during each foal's focal samples,(mean ±SE) 69 ± 2 % of the snappings would have been directed towardadults and 31 ±2 % of the snappings would have been directed toward othertoals. Instead, 93 ±3 %ot the snappings were directed toward adults and7 ± 3 % of the snappings were directed toward other foals. Thus, foals snapped to ponies one year old or older more often than expected and to other foalsless often than expected (sign test, p < .001).

46 s. L. CROWELL-DAVIS, K. A. HOUPT and J. S. BURNHAM

Of a total of 43 incidents of snapping by one foal to another, 14 occurredimmediately after an aggressive act by the latter. On four occasions, the foalthat was snapped to aggressed against the snapper only after it had beensnapped at. Twice the snapping was followed by mutual-grooming. On oneoccasion it appeared in a multiple foal interaction involving mutual-grooming.Two fillies were mutual-grooming when a colt approached them and theyceased mUftial-gf66ffiiiig. The felt then snapped to one filly and began grooming the other. Both fillies immediately laid their ears back to the colt, whichleft. On two occasions, a foal snapped to a mare, then snapped to that mare'sfoal. On one occasion, two foals snapped at each other at the same time. Themajority of the other incidents came under the category of spontaneous snapp-

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ing. This occurred both when foals had already been standing or feedingbeside each other and when the foal which snapped approached another. Onsome of these occasions, nosing by one or both of the foals preceded thesnapping or occurred during it.

c. Rate

Median values rather than means were determined for rate because theextreme values (based on one colt: see below) severely distorted the values formeans. The overall median rate by the 20 foals for which data were availablethrough at least 18 weeks of age was 0.23 times per h or once every 4.4 h.Snapping occurred once every 10 h during weeks 1 to 4 of life and peakedat once every 3.2 h during weeks 5 to 8. Snapping occurred only .05 timesper h or once every 20 h during weeks 21 to 24. However, only small datasets were available on a few individuals during the latter period. Therefore,the figure may be artificially low. Values were intermediate during the inter-vening periods (Fig. 2). .

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Fig. 2: Median rate of snapping by foalsat various ages. Values are based on foalsfor which there were at least 4 h of focalsample observations on the foal and itsmother during a given 4-week period. Theage of the foal is given in the lowerabscissa. The number of foals used to determine the median is in the upper abscissa

D. Sex Differences in Rate of Snapping

There was no significant difference in the overall snapping rates of the12 fillies and 8 colts that were observed to at least 18 weeks of age (MannWhitney p>.10). There was, however, a large range in snapping rate, especiallyamong colts. Values for colts ranged from 0 for one colt who was neverobserved to snap during his own focal sample sessions, to once every 0.4 h foranother colt. The colt with the calculated snapping rate. of 0 was observed tosnap at other times than during his focal sample sessions, and so merely snappedrarely rather than not at all. For fillies, the range was once every 1.6 h to onceevery 50 h. If the data are evaluated only as simple count data, withoutallowing for individual differences, colts appeared to snap much more often


than did fillies. During 296.4 h of observations, focal colts snapped 211 times,whereas during 510.9 h of observation, focal fillies snapped only 128 times.However, over half of the snapping by colts was done by one colt and thetwo colts with the highest rate together accounted for 3/4 of the total snappingby colts. The other 6 colts snapped within the same range of rates as the fillies.

E. Sexof Adults to which Foals Snapped

In order to determine whether foals snapped more to stallions than wouldbe expected under the assumption that they snapped randomly to either sex,expected values for snapping to mares or stallions were calculated from snapping to adults during a foal's own focal sample when a stallion was present.Results differed for colts and fillies.

A total of 60 snappings by 5 colts occurred for which the expected valuefor snapping to a mare or to a stallion was at least 1. If colts were snapping .randomly to all adults present in the pasture, 21 ± 3 % of the snappings toadults would have been directed toward the stallion and 79 ± 3 % toward amare. Instead, 51 ± 9 % were directed toward the stallion and 49 ± 9 % weredirected toward a mare. Each colt snapped more to stallions than was expectedand less to mares than was expected (sign test, p = .03).

A total of 54 snappings by 8 fillies occurred for which the expected valuefor snapping to a mare or to a stallion was at least 1. There was no significantdifference between observed and expected values (sign test, p = .23).

F. Approaches

In about half of the snappings (54 ± 6 %), the foal and the pony itsnapped to were already beside each other when the snapping occurred. Thiscame about in a variety of situations. For example, they may have been restingupright beside each other, grazing side by side, or playing together. In aboutone fourth of the incidents (24 ± 3 %), the pony that was snapped to eitherwalked directly toward the foal or was walking past it when the foal snapped.During the other fourth of the incidents (21 ± 5 %), the foal approached thepony, which it subsequently snapped to. Rarely, both ponies approached eachother immediately prior to the snapping (1 %).

G. Aggression

In 62 ± 5 % of the cases, no aggression was directed toward the foalimmediately before, during, or immediately after the snapping. In 31 ± 5 %of the cases, snapping began after the initiation of an aggressive act towardthe foal. In 7 ± 1%of the cases, an aggressive act toward the foal began onlyafter the foal began snapping. Rarely, a pony would carry out aggressionagainst the foal, the foal would snap, and the pony would initiate one or moreadditional aggressive acts (1 %). For colts, there was no difference betweenmares and stallions in the likelihood that the adult would have shown aggression before the incident, after the incident, or not at all (x2 = 3.16 P > .10).For fillies, however, there was a difference (xt = 11.22 P < .005). Snapping


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by fillies to stallions was more likely to occur without there having been anyaggressive behavior on the part of the stallion. Snapping by fillies to mareswas most likely to occur after aggression by the mare. As with colts, maresand stallions were equally likely to respond to a filly's snapping by carryingout aggression against her. The likelihood that the snapping would follow anaggressive act or that an aggressive act would follow snapping did not dependon which pony initiated the approach (X2 = 0.26 P > .5).

H. Nosing

Nosing, that is, bringing the nostrils close to or touching the body ofanother pony, was observed on several occasions, both by the snapping foaland by the pony snapped to. The foal might nose a pony, or approach it andnose it, then snap, whether the other pony had reacted to the foal or not.Nosing by the pony snapped to occurred both immediately before and immediately after snapping. It was the typical reaction of stallions when a youngfoal approached them and snapped (Fig. 1).

I. Maternal Responses to Snapping

Foals snapped to their own mother on 33 occasions. On 8 occasions itwas ambiguous whether the foal was snapping to the mare, the stallion, orboth. Of the remaining 443 snapping incidents 15 were followed by a distinct,immediate response by the mare. Of these, 12 involved aggression by the maretoward the pony snapped at. Two involved the mother moving between thefoal and the pony snapped at, while the other involved a vocalization by themare which was followed by the foal returning to her. Mares exhibited aggressive behavior toward the pony snapped to after snapping by their foal toother mares, foals, geldings, and stallions.

J. Snapping during Courtship

Snapping was observed 16 times during courtship activity between thefoal's mother and the stallion. In some cases the snapping was clearly directedtoward either the stallion or the mare, while in other cases it was ambiguouswhether the snapping was directed toward either individual in particular.Since foals were observed to snap to their own mothers under other circumstances than courtship, it could not be assumed that the foal was snappingto the stallion. 12 of the snappings during courtship occurred during the foal'sfirst 4 weeks of life.

K. Behavior of Foals after Snapping

The behavior of foals after snapping was highly variable. Often theywould resume what they had been doing immediately prior to snapping: feed-ing, Walking abeut @fllI6fing, llhying, @tc. On 46 oef~§iOfl§, the f8~1 movedaway from the pony it had snapped to immediately after snapping. The gaitvaried from a walk to a canter. On 10 of these occasions, the foal returned toits mother. Alternatively, foals backed away from the pony (7 occasions), or

z. Tierpsychol., Bd. 69t Heft t 4

50 s. L. CROWELL-DA\·IS, K. A. HOUPT and J. S. BURNHAM

simply turned away (3 occasions). In turning away, the foals did not movefar, but shifted their body position so that their head and neck were fartherfrom the pony than their hind-quarters. On 3 occasions, the foal immediatelyfollowed the pony snapped to or walked by its side, although it had not beendoing so before the snapping. On 6 occasions, the foal began grooming theother pony..This occurred 3 times to another foal, twice to a stallion, andonce to the foal's mother.

L. Snapping after Aggression by Foal

On four occasions, foals combined aggressive behavior with snapping.For example, a colt approached a 2-year-old mare who was grazing and bither neck. The mare lifted her head and the colt immediately snapped at her.

Discussion

TYLER (1972) and BOYD (1980) both noted that snapping had no effecton inhibiting aggressive behavior on the part of older animals. In the currentstudy, it was found that snapping sometimes triggered aggression. In addition,foals often approached older animals and then snapped to them. TYLER (1972)commented that foals often approached adult mares or stallions and snappedwithout provocation. Subsequently, mares usually threatened the foals, whichthen moved away. Stallions observed by TYLER were less likely than maresto threaten a foal that snapped at them. In the Ethological Dictionary, submissive behavior is defined as "Behavior of subordination in order to preventattack; defensiveness" (HEYMER 1977). In a number of cases in various studiessnapping has not fit these criteria and ZEEB'S (1959) interpretation that snapping is a gesture of submission may have been premature.

ZEEB (1959) also suggested that snapping was a form of inhibited mutualgrooming. However, the two behaviors are very different. When foals approach each other or adult ponies prior to mutual-grooming, they almost invariably have their heads up and their ears pointed forward, which contrastsmarkedly with the lowered heads and ears characteristic of snapping. Grooming movements" either of the biting or scratching kind, are characterized bybrisk movements of the head, whereas in snapping the head is relatively still.While the mouth is open most of the time once grooming commences, thecommissures of the lips are not retracted as they are in snapping. Flexion ofthe carpus was never observed during mutual-grooming.

Based on observations made in this study and descriptions of comparablebehaviors made in other studies, we propose that snapping is ritualized nursingbehavior which occurs as a displacement activity in circumstances of conflicting drives or excess excitation.

Nursing, like snapping, is characterized by extension of the head andneck, with frequent turning of the ears to the side (Fig. 3). ROSSDALE (1967)first recorded foals as making a characteristic "champing" movement of thejaws during the first hour of life. TYLER (1972) subsequently reported that

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snapping was one of the first behavior patterns seen in a foal a few minutesafter parturition. In the current study" during close-up observations of initialmotor patterns of nursing, it was noted that foals often made movements oftheir jaws similar to those of snapping just before reaching for the teat or asthey were attempting to take hold of it. STEBBINS (1974) observed that Appaloosas frequently rotated their heads when snapping. By including this rotation of the head, the Appaloosa foals almost reproduced the action of takingthe teat in the mouth.

Displacement activity has been defined as "Excess excitation which cannot be released through normal channels". Further, "The most frequent causesare conflicts between opposing drives, as for example, the conflict during afight between attack and flight ... Usually the resulting behavioural responsesare elements which normally occur very frequently, e.g, feeding behaviour,comfort movements, resting postures" (HEYMER 1977).

WOLSKI et ale (1980) observed snapping by foals during tests in which thefoal had been separated from its mother and either the mare was restrainedwhile the foal was required to find her as opposed to an alien mare Of" conversely, the foal was restrained while a mare sought her own foal. TYLER

(1972), BOYD (1980), and STEBBINS (1974) all observed snapping in foals whichhad Become separafed frBfti their ftiodier~. Iii fhe~e iasnnees either ej{Eessexcitation or a conflict between the desire to approach a possible mother andthe desire to avoid a possibly unfriendly animal could have triggered thesnapping.

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Following are other examples of contexts in which snapping has beenobserved in which an approach/avoid or remain near/avoid conflict could be.occurring.

1. Snapping by hand-raised orphan foals when approached by strange humans(WILLIAMS 1974).

2. Snapping to cattle (TYLER 1972; WILLIAMS 1974).3. Snapping by foals of blind mares to their mother when she is restrained

and repeatedly whinnies (HOUPT, pers, obs.),4. Snapping by foals during courtship of their mothers (TYLER 1972; STEB

BINS 1974; Current study).5. Snapping by young mares when being tended by stallions during their

first oestrus (TYLER 1972; STEBBINS 1974).

The fact that has been most consistent in all reports of snapping behavioris that it is a behavior of young animals. It is most common in foals, declinesrapidly in rate of occurrence after an animal reaches one year of age, anddisappears by the fourth year of age. Nursing also follows this pattern. Foalsnurse less frequently as they grow older. 'I f their mother has another foal thefollowing year, she will usually prevent further nursing by her yearling. However" if she does not have another foal, the yearling will continue nursing at adepressed rate (TYLER 1972; DUNCAN et ale 1984). Rarely, sporadic nursingmay continue into the animal's third year of life (KEIPER, pers. comm.). Incontrast, true submissive gestures such as avoiding and turning the head awaycontinue throughout adult life.

The rate of snapping did not correspond to increasing contact with otherponies. Snapping peaked at weeks 5-8, then decreased in rate, whereas contact with ponies other than the mother increased steadily throughout the study(CROWELL-DAVIS 1983). It may be that foals pass through a major socialization phase or critical period during their second month of life, such as thatwhich occurs in dogs (SCOTT and FULLER 1965) and that the peak in snappingis one effect of this phase. The foals appeared to be intensely responsive toeven mild social cues from other ponies during this period.

The disproportionate snapping by colts to stallions may reflect earlytendencies towards social behaviors congruent with their adult life-styles inthe feral state. Among feral horses colts interact with other males primarilyby combat, either ritualized "play" combat or serious fights which result ininjuries (PELLEGRINI 1971; TYLER 1972; KLINGEL 1974; KLINGEL 1975; FEISTand MCCULLOUGH 1976; KEIPER 1976; BERGER 1977; GATES 1979; WELLS andGOLDSCHMIDT-ROTHSCHILD 1979; RUBENSTEIN 1981). Colts do not associatewith stallions more than do fillies (CROWELL-DAVIS 1983). However, coltsmay be more intensely stimulated by the presence of a stallion than fillies areas the tendency to engage in combat develops in them.

Snapping probably does communicate information about the foaPs emotional state to other ponies, or at least to the mother. This is indicated by thecases in which the foal's mother reacted in a manner to defend the foal. Thefact that this reaction by the mare was rare suggests that mares tend to allow

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their foals to learn appropriate social responses on their own. Given the greatvariation of context, and of behavior of the foal and other ponies followingsnapping, it is possible that, as regards providing a signal to other ponies,snapping has multiple functions, depending on context, or perhaps has nosignal function at all.

Zusammenfassung

Unter verschiedenen Umstanden schnappten Fohlen (mannliche und weibliche gleich haufig) nach jungen und ausgewachsenen Ponies, selten jedoch nachanderen Fohlen. Mannliche Fohlen schnappten ofter als erwartet nach einemHengst, weihliche schnappten ohne Unterschied nach heiden Geschiechtern. In62 ± 5 % der Falle war kein aggressives Verhalten gegen das Fohlen gerichtet.Es gab gegenseitiges Nasenreiben zwischen Fohien und ausgewachsenen Tierenvor und nach dem Schnappen, Wenn das eigene Fohlen nach .einem Ponyschnappte, zeigten Stuten gelegentlich aggressives Verhalten gegen das Pony.Es scheint, daf Schnappen verschiedene Funktionen haben kann, je nachZusammenhang, und daf es sich dabei urn eine Ubersprungbewegung vonFohlen und jungen Pferden handelt, die vom Saugeverhalten herstammt,

Acknowledgements

We would like to thank Mr. and Mrs. K. BUTLER for allowing the use of their farmas a study site. C. CARINI, ]. CAL'iEVALE, and L. KANE assisted with the data collection.Dr. G. HAUSFATER provided much useful advice during the course of this study. Preparationof this paper was supported in part by VMES Grant 84-118.

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54 s. L. CROWELL-DAVIS et al., Snapping by Foals of Equuscabalius I1

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Authors' addresses: .S. L. CROWELL-DAVIS, College of Veterinary Medicine, Univ. ofGeorgia, Athens, Georgia 30605, U.S.A.; K. A. HOUPT and ]. S. BUR~!iAM, New York StateCollege of Veterinary Medicine, Cornell Univ. Ithaca, New York 14850, U.S.A.

Snapping by Foals of Equus caballus

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