Antorbital and forehead secretions of black-tailed deer (Odocoileus hemionus columbianus): Their role in age-class recognition

Anim. Behav ., 1978,26, 1 098-1106

ANTORBITAL AND FOREHEAD SECRETIONS OF BLACK-TAILED DEER (ODOCOILEUS HEMIONUS COLUMBIANUS) : THEIR ROLE IN AGECLASS RECOGNITION BY N. J. VOLKMAN, K . F. ZEMANEK* & D . MULLER-SCHWARZEt Department of Zoology, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210

Abstract. Male black-tailed deer (Odocoileus hemionus columbianus) scent mark with their forehead gland secretion and antorbital sac contents . When forehead and antorbital sections were presented on the same nylon rod on an artificial tree, male deer discriminated between male yearlings' and fawns' secretions . When the secretions were presented separately, male deer discriminated between yearlings' forehead and antorbital secretions and blank controls . Discrimination was indicated by differential rates of sniffing and licking . In addition, the frequency of forehead rubbing of the scent marks appeared to be dependent on the dominance relationships of the male deer . Chemical evidence is presented which suggests that male yearlings' and fawns' antorbital secretions differ quantitatively . Females did not respond preferentially to these secretions and, with the exception of sniffing, responded significantly less than males . Mammalian olfactory signals have several functions, including recognition of individuals, species, sex, group and social status (see Ralls 1971 ; Eisenberg & Kleiman 1972 ; MullerSchwarze 1974 ; and Thiessen & Rice, 1976) . Olfactory signals originate from several sources : secretions of sudoriferous and sebaceous glands, urine, saliva and faeces . Scent marking with more than one source of odour is common among mammals, although experimental analyses of multiple olfactory signals are limited . The most detailed of these are the studies on Helogale (Rasa 1973) and Orcytolagus (Mykytowycz 1966 ; Goodrich & Mykytwoycz 1972) and Petaurus (Schultze-Westrum 1965, 1969) . When scent marking tree branches and shrubs, black-tailed deer (Odocoileus hemionus columbianus) use at least two sources of olfactory signals, the forehead glands and the antorbital sacs . Muller-Schwarze (1971, 1972) described forehead and antorbital rubbing and discussed the significance of forehead rubbing in captive black-tailed deer . Quay & Muller-Schwarze (1970) found the forehead skin to be characterized by interwoven collagenous fibres, but few sudoriferous or sebaceous glands . The forehead has a faint odour and forehead scent marks are odourless to humans, although dogs can be taught to find sticks forehead-rubbed by white-tailed deer (0. virginianus) (Moore & Marchinton 1974) . The antorbital sac, a thinwalled diverticulum located just anterior to the eye, is composed of a small amount of glandular

tissue, and a thick waxy material partially fills the lumen (Quay & Milller-Schwarze 1970) . This material is brownish yellow and has the odour of very ripe soft cheese. It may be composed of glandular secretions, accumulated sloughed epidermal cells, and bacterial byproducts, or a combination of these . Although it is more accurate to label the antorbital sac material as its `contents' we use the term antorbital `secretion' for simplicity. The goal of this study was to determine if the antorbital and forehead secretions play any role in the discrimination of age classes by black-tailed deer . Materials and Methods Animals Eight hand-raised black-tailed deer were used in these experiments . Four were 1.5-y old `yearlings' : two males, B and G ; and two females, D and L . Four were 6-month-old : two males, J and K ; and two females, 'fawns' N and O. The deer were housed in varying social groups in 17 x 40 m wire pens. Male G was housed with females D and L ; male B, with a fawn that was not used in these experiments ; males J and K, with females N and O . Male B was in visual contact through a shared wire fence with males J and K and females N and O . All groups were socially well integrated . The deer were maintained on an ad libitum diet of Agway deer pellets . CMD No . 888, alfalfa hay and water, rolled oats during the winter, grasses and forbs when they were available in the pens, and occasionally apples .

*Present address : Department of EPO Biology, University of Colorado, Boulder, Colorado . tReprint requests to D . Muller-Schwarze . 1098

VOLKMAN ET AL . : ANTORBITAL AND FOREHEAD SECRETIONS OF BLACK-TAILED DEER

Sample Collection and Presentation Four stimuli were used : forehead secretion (FH), antorbital secretion (AO), and a combination of forehead and antorbital secretions (FHAO), and no secretion as control . A set of three samples on white nylon rods on the branches of an artificial tree was presented to the deer. The three samples were : a secretion from a male yearling, the same secretion from a male fawn, and a clean rod (internal control) . In addition, sets of three clean rods were presented as external controls . Within each sample set the position of the juvenile, fawn and control rod was systematically rotated throughout the experiment. An antorbital secretion was collected by slowly rotating the tip of a rod three times in a sac ; a forehead secretion by vertically rubbing and slowly rotating a rod 10 times on the forehead of a deer ; combined forehead and antorbital secretions by first collecting the forehead secretion and then the antorbital secretion, in the above manners. Nylon rods were always handled with disposable plastic gloves and washed after each experiment in an automatic dishwasher . Male yearlings, B and G, and male fawns, J and K, served as secretion donors. Each male received the secretions of the other male deer of its own age class and, in random order, the secretions of the two males of the other age class. Females received the secretions of the two yearlings and the two fawns in random order . All receivers were tested six times with each of the three secretions and six times with the external control set . Experimental Apparatus : Artificial Tree An artificial tree was constructed to provide a sample holder so that the deer could reach only the three white nylon rods and no other part of the tree could be marked or investigated, Two 3-m long cedar posts were secured in the ground outside of each pen, I m from the wire fence . A 4-m long, 5 . 1 x i0 . 2-cm board was supported horizontally . at a 45 0 angle on triangular braces mounted 2 m above the ground on the cedar posts. Three 2-m long, 2 . 5 x 2 .5-cm oak sticks were held on the board 1 m apart by U-bolts and inserted through the fence into the pens . The board was strapped to the triangular braces with ski straps to give the oak sticks some mobility if pressure were applied by a deer. Polyvinylchloride (PVC) tubes, 0 . 5-m long, through which two holes had been drilled, were slipped over the ends of the oak sticks .

1 099

White nylon rods, 15 cm long and 1 cm in diameter, were inserted through the holes in the tubes and the oak sticks. The PVC tubes served both to hold the nylon rods in place and to protect the ends of the oak sticks from contamination . The height of the nylon rods was adjusted by sliding the oak sticks up or down and then securing them to the 5 . 1 x 10 . 2-cm board with a nail placed through a hole in the oak sticks and through an eye screwed into an edge of the board. Each nylon rod projected downward at an angle of 20° from the vertical and was placed at a level accessible to an individual deer (see Fig . 1) . - Procedure Two experimenters conducted the tests . Prior to each trial, the experimental area inside the pen was closed to all deer. If sample sets were being presented, secretions were collected from the donors and temporarily placed in a wooden holding board. The three oak sticks were then inserted through the U-bolts and adjusted to the height suitable for the deer being tested . The nylon rods were then placed in their assigned positions through the holes in the PVC tubes and oak sticks . The same procedure was followed for external control sets, except that three clean rods were used. One person allowed the receiver deer into the experimental area as soon as the other, the observer, was in position, and quickly left the area . The observer recorded the deer's behaviour on a portable tape recorder

1 9 A

Fig . 1 . Artificial tree showing white nylon rod (A), PVC tube (B), oak stick (C), and recorder (D) .

1 100

ANIMAL BEHAVIOUR, 26, 4

from a position 5 m from the fence line, facing the centre of the artificial tree . The deer was attracted into the experimental area by tossing apples into the area ; the more tractable deer were herded . The time that elapsed between collection of a secretion and the beginning of the experiment ranged from 3 to 5 min . Each experiment was run for 5 min from the first response to any nylon rod . This usually occurred within 1 min after secretions were in place . The frequencies of the following responses to the nylon rods were recorded Sniffing (SN) : each movement of the external nares when within 0 . 5 cm of a rod . Licking (LK) : each movement of the tongue across the surface of a rod . Forehead rub (FHR) : each movement of the forehead on a rod . Antler thrash (ATR) : each contact of any part of an antler on a rod. Antorbital rub (AOR) : each movement on a rod of the area in or around the antorbital sac . Antorbital spread (AOS) : each opening of the antorbital sac . Mouthing (M) : each movement of the mandible when a rod was in the mouth of a deer, including contact with lips, tongue or teeth . Experiments were run from mid-December through January, the reproductive season of young deer. Each receiver was tested once a day . Experiments were performed in all types of weather, except blowing snow with poor visibility. Temperatures on experimental days ranged from - 20 to + 4° C. Because deer are polyphasic and their activity cycles are influenced by prevailing weather conditions, experiments were performed during daylight hours on an opportunistic basis . No experiments were begun if a receiver animal were lying down, although collections were taken from reclined deer .

the Kruskal-Wallis test was followed by the procedure developed by Dunn (Hollander & Wolfe 1973) for multiple comparisons, to determine significant differences between pairs within the population . To adjust for varying levels of responsiveness, the frequencies of responses were divided by their corresponding internal control frequencies . Then, individual deer or secretions were compared . Results The initial order of investigative and marking responses to a rod in this experiment consisted of sniffing, licking, mouthing, antorbital rubbing (during which the sac was either spread or remained closed), forehead rubbing, and antler thrashing. If the deer continued to mark, the order of responses varied . Combined Male Yearling sand Male Fawn Responses Male fawns sniffed, licked, forehead rubbed, and mouthed, but did not antorbital rub, antorbital spread or antler thrash . Consequently, only the frequencies of the former responses could be combined for both age classes . Statistical analysis (Kruskal-Wallis) of responses to external controls indicated that males did not show a preference for any position on the artificial tree . There was significantly more sniffing and licking/nylon rod during FHAO, FH, and AO trials than during external control trials . Forehead rubbing was significantly higher during FH trials than during external control trials, but not during AO nor FHAO trials (P < 0 .09, see Fig . 2) . Mouthing during FHAO, FH and AO trials did not differ from those of external controls . a

FH AO

FH

AO

External Control

0 14 T C

Statistical Analyses Since samples were repeatedly presented to the deer a two-tailed Mann-Kendall test for trends (Hollander & Wolfe 1973) was applied to the data of individual deer in order to determine if the data were random samples from common populations. No significant trends were evident . The Kruskal-Wallis one way analysis of variance by rank for multiple samples was then performed on each variable (SN, LK, FHR, ATR, AOR, AOS, M) for each population (yearling, fawn, internal control) of the three secretions (FHAO, FH, AO) . Whenever significant differences were found within a population

0

12

11.1 .,

Ito . * 010 a

62 . 7.3

0>, 6 c

65 . . S6

I

4

43 30

2.4 1.9

2

5n Lk F r

M

Sr LK Fir M

Sn Lk Fhr h1

Sn Lk Fhr M

Fig . 2. Males : mean frequencies of responses/nylon rod for secretions (FHAO, FH, AO) and external controls. Levels of significance of difference from external controls ***=P<0.001,**=P<0 .01 ;*=P<0-025 .



VOLKMAN ET AL . : ANTORBITAL AND FOREHEAD SECRETIONS OF BLACK-TAILED DEER

Significant differences were found in all populations of FHAO, FH and AO for sniffing and licking, but significant differences for forehead rubbing were found only in FHAO populations . Analysis of pairs within populations revealed significantly higher frequencies of sniffing and licking of yearlings' FHAO secretions than of fawns' FHAO secretions ; significantly higher frequencies of forehead rubbing of yearlings' FHAO secretions than of internal controls ; and significantly higher frequencies of sniffing and licking of yearlings' FHAO, FH, and AO secretions than internal controls (Table I) . Only the sniffing of the fawns' FH secretion was significantly higher than that of the internal controls . Comparison of Male Yearling and Male Fawn Responses Male yearlings and male fawns sniffed and licked all secretions at similar rates . The only difference between the two age classes was the rate of forehead rubbing of fawns' FH secretion by male fawns . Male fawns forehead rubbed these secretions more frequently than did male yearlings, but not significantly more (P < 0 .053) . Comparison of Individual Male's Responses No significant differences were seen between any of the responses of the two male fawns . In contrast, the male yearlings differed in their frequencies of forehead rubbing and antler thrashing . Yearling B forehead rubbed the yearling's FHAO secretions five times more than

1 10 1

internal controls, and antler thrashed them 5 .7 times more than the internal controls . Yearling G forehead rubbed yearling's FHAO secretions 0.7 times less than the internal controls and antler thrashed them as often as internal controls . Male B forehead-rubbed and antlerthrashed yearling's FHAO secretions significantly more than male G (P < 0 .025) . In addition, there was a trend for male G to sniff yearling's FHAO secretions more frequently than male B (P < 0.055) . Combined Female Yearling and Female Fawn Responses Thresponses observed and analysed for females were sniffing, licking, forehead rubbing and mouthing. No female showed a preference for any position on the artificial trees during external control trials. Females sniffed significantly more in FHAO, FH, and AO trials than in external control trials (Fig . 3). Licking, forehead rubbing and mouthing were as frequent as in the external control trials . Females sniffed yearlings' FHAO, FH and AO secretions more frequently, but not significantly more often than fawns' secretions or internal control rods (Table II) . Licking, forehead-rubbing and mouthing were rare and directed at all three rods and all three secretion types . The female fawns responded more strongly than the female yearlings, with negligible individual differences for either fawns or yearlings .

Table L Mean Frequency of Combined Mate Responses to Secretions and Internal Controls

Secretion Response

Combined Forehead-antorbital

Antorbital

Forehead

Control Yearling

Fawn

Control

Yearling

Fawn

Sniffing N = 24

14 . 7 bl

11 . 8 cl

6 .8

16 . 7 bl

10 . 6

9. 1

21 . 5 a1, bt

10 . 6

8.5

Licking N = 24

13 . 6 bi

7.3

3 .6

17 . 0 b2

9.5

4.4

23 . 8 al, bl

6. 1

3.0

Forehead rubbing N = 24

7.8

8.6

3. 1

6.7

5.9

4.3

9.3 b3

4 .0

3 .6

Mouthing N = 24

2.8

3 .0

1 .4

l •9

1 .5

2 .4

3 .3

l •2

1 .2

a : Significant difference between responses to yearling and fawn secretions . b : Significant difference between responses to yearling secretions and internal controls. c : Significant diffciciice between responses to fawn secretions and internal controls . 1 : P < 0.001 . 2 : P < 0 . 01, 3 : P < 0 . 05 .

Fawn

Control

Yearling



1 102

ANIMAL BEHAVIOUR, 26, 4

licked the yearlings' secretions 12 times more frequently than females (P < 0 .001) ; the fawns' secretions, four times more (P < 0-01) ; and the external control rods, three times more. Males forehead rubbed the yearlings' secretions nine times more than females (P < 0 .001) ; the fawns' secretions two times more (P < 0 .05) and the external control rods seven times more (P < 0 . 01).

Comparison of Combined Male and Combined Female R Females never antorbital rubbed or antorbital spread in response to test stimuli. Because no significant differences were found among FHAO, FH, and AO secretions for the combined data of either sex (see below), males' and females' responses to both the yearlings' and the fawns' secretions were analysed and compared in the following manner . The means of the males' and females' responses to the yearlings' and the fawns' FHAO, FH, and AO secretions were divided by the mean of the internal control responses for all three secretions to yield internal control-corrected frequencies (Fig . 4) . Females' and males' external control frequencies were compared directly (see Figs. 2 and 3) . Males sniffed both yearlings' and fawns' secretions more frequently than females, although the differences were not significant . However, males sniffed external control rods twice as often as females (P < 0 . 01) . Males P s

FHAO

FH

AO

Comparison of Sample Types Although most responses to FHAO secretions were stronger than those to FH and AO secretions, on only three occasions were these differences significant . Taken together, the male yearlings, G and B, sniffed yearlings' FHAO secretions significantly more than yearlings' FH secretions (P < 0 .001) but not more than yearlings' AO secretions . Response differences to AO and FH secretions were not significant . Only male yearling G sniffed yearlings' FHAO secretions more frequently than yearlings' AO secretions (P < 0 .05), but not more frequently than yearlings' FH secretions . Again, response differences to FH and AO secretions were not significant . Male fawn J forehead rubbed yearlings' FHAO secretions more frequently than yearlings' FH secretions (P < 0 .05), but not yearlings' AO secretions . Response differences to FH and AO secretions were not significant .

External Control

0 c s a

fi5 .

&1 ~ +

V C

Discussion Our experiments demonstrate that male blacktailed deer discriminated between yearlings and fawns on the basis of antorbital and forehead secretions, when these secretions were presented simultaneously. When yearlings' FH and AO secretions were presented separately, they were readily distinguished from internal controls . Of the fawns' secretions, however, only the

4

S 2

13 02

11

2.1 1A ®

1.5

15

1.3

~5 Sm LK Fhr M

Sn Lk Fhr M

Sm Lk Fhr M

'

®4 ~ Sn Lk Fhr M

Fig. 3. Females : mean frequencies of responses/nylon rod for secretions (FHAO, FH, AO) and external control. Level of significance of difference from external control : ** = P < 0 .01 .

Table II. Mean Frequencies of Combined Female Responses to Secretions and Internal Controls

Secretions Response Sniffing N = 24 Licking N = 24 Forehead rubbing N = 24 Mouthing N = 24

Yearling

Fawn

Combined Forehead-antorbital

Antorbital

Forehead Control

Yearling

Fawn

Control Yearling

Fawn

Control

9.7

4.5

5 .5

6.1

5.3

5.7

7.4

5.4

5 .6

1-2

1-7

1-3

1 .1

1-4

2.1

0.68

0.4

2-8

0-08

2 .0

0.5

0-04

0.9

0. 7

0 .2

0.4

0.2

1-5

2-0

1 .0

1 .0

1-8

3-5

1-4

0-3

2-2

VOLKMAN ET AL. : ANTORBITAL AND FOREHEAD SECRETIONS OF BLACK-TAILED DEER

forehead secretions were responded . to differentially from internal controls . The deer did not respond differentially to FHAO, FH and AO secretions . Age class discrimination by male deer was indicated primarily by the sniffing and licking responses . In addition, male deer did forehead rub the yearlings' FHAO secretions significantly more than the internal controls. It is possible that the combined male data did not show that males forehead rubbed yearlings' secretions more than fawns' secretions because of dominance relationships among the males. MullerSchwarze (1972) found that dominant males forehead rubbed more than subordinates . A previous experiment showed that male yearling B had been dominant to male yearling G, and our data showed that B forehead rubbed yearlings' FHAO secretions more than G (P < 0.025) ; no data were available on the dominance relationship of the two male fawns . However, while male fawn K forehead rubbed FHAO, FH and AO secretions equally often, male fawn J tended to mark yearlings' FHAO secretions more frequently than fawns' FHAO secretions (P < 0 . 01) . When the forehead rubbing frequencies of male yearling B and male fawn J were combined, the resultant data showed that B and J discriminated between the yearlings'

Yearling

Fawn

K

E Sn

Lk

Fhr

Sn

Lk

Fhr

Fig. 4. Males vs. Females : mean control-corrected frequencies flsi rod for diffetenc e FH, AO). .LLevels / o significance of differee ) between male and female responses : *** = P < 0 . 001, ** = P < 0 .01, * = P < 0-05 .

1 103

and fawns' FHAO secretions (P < 0 .05), between yearlings' FHAO and the internal controls (P < 0 . 01), but not between fawns' FHAO and internal controls . B and J also forehead-rubbed the yearlings' FHAO secretions significantly more than G and K (P < 0. 05). These results suggest that dominant males in a group tended to forehead rub the male yearlings' secretions . On the other hand, both dominant and subordinate males sniffed and licked the yearlings' secretions more than the fawns' . If the possible dominance relationships are considered important, the discrimination of yearlings and fawns on the basis of FHAO secretions has been demonstrated for both passive (sniffing and licking) and active (forehead rubbing) responses . The females' responses to any of the secretion types did not suggest discrimination of age class . However, all three secretions were sniffed significantly more than those of the external controls . That females did not discriminate age classes does not necessarily imply that no information was transmitted to them by these secretions. Females might have obtained information without preferentially sniffing a scentmark . Sniffing, licking and mouthing were universal responses . When frequencies were corrected with internal control scores, only the licking and forehead-rubbing responses were significantly higher for males than for females . The lack of antorbital rubbing and spreading by male fawns and both age classes of females suggests hormonal control of these behaviours . Forehead rubbing by males occurred 9 times more than by females and was observed in almost the same ratio, 8 : 1, by Muller-Schwarze (1972) . Its function in females cannot yet be ascertained. The results of bioassays on captive animals should be interpreted with regard to two importtant variables : the artificiality of the bioassay and the composition of the secretions being tested . Perhaps the most important artifact of this bioassay is the limit of 5 min. No data are available on the amount of time wild deer investigate and mark scent posts . In our trials, males spent most of each trial period investigating samples and little habituation was observed throughout the tests . Females rarely spent more than a quarter of the time investigating samples . It is possible that the deer's ability to discriminate age classes only when the two secretions were presented simultaneously was a function



1 104

ANIMAL BEHAVIOUR, 26,

of the amount of information available to them within a limited span of time . Ideally, the quality and the quantity of all bioassayed materials should be known. In practice, as pointed out by Doty & Dunbar (1974), this goal is seldom obtained. There are two approaches to this problem, analytical chemistry and controls within the experiment as done by Epple (1971) . Chemical techniques such as gas chromatography are usually employed only after preliminary behavioural results have been obtained . Epple's approach, the use of the glands of both single donors and pairs of donors, presents problems when the quantity of the materials on the glands are unknown . Doubling the number of glands used can be inadequate if one type of animal's gland contains substantially more than twice that of another's . There is also the possibility of overkill, that the response to a chemical compound may change with concentration . Preliminary gas chromatographic analysis of black-tailed deer's antorbital secretions by A. Claesson (unpublished) indicates that yearlings' secretions contain six to eight peaks in the volatile range, while fawns' secretions contain comparatively small peaks in the same range (Figs . 5a and b) . Correspondingly, male fawns do not antorbital rub . Because the sacs are not highly glandular in black-tailed deer, the origin of the material that partially fills the lumen has not been determined . Quay and Muller-Schwarze (1970) suggested that the material is the result of orbital drainage and sloughed epidermal cells . The material in many mammalian sac-like structures, in particular anal glands, has been thought to be the metabolic by-products of symbiotic bacteria (see Albone & Perry (1976)) . This is a possible source of the antorbital sac material of the black-tailed deer. Recently, Thiessen & Rice (1976) have hypothesized that cervid antorbital gland material originates from Harderianlacrimal glands. Antorbital glands are present in all species of cervids with the exception of Moschus. MullerSchwarze (1975), in his brief review of cervid antorbital marking, noted that while many species use the organ in threat behaviours, few species, such as Cervus duvauceli, Axis axis, and C. eldi thamin, distinctly mark objects with them . Chemical analysis of the forehead secretions was not attempted because no material from the forehead can be smelled, felt or seen . However,

4

fawns' forehead secretions may be qualitatively different from those of yearlings because males only sniffed the fawns' forehead secretions significantly more than internal controls . In addition, male fawns J and K tended to forehead rub the fawns' forehead secretions more than male yearlings' B and G (P < 0 .01) . While forehead secretions have been observed to be used only in the context of scent marking, black-tailed deer use their antorbital sacs in a number of contexts . During threat displays males and females spread their antorbital sacs, and the secretions are easily visible to an observer. Fawns open their sacs while nursing, although no secretions are visible. It is not known whether these signals are visual, olfactory, or both . These experiments thus indicate that as far as is known, the social functions of these secretions in the context of scent-marking might be similar . The fact that male deer discriminate age classes readily when the two secretions were presented together, but not when they were presented separately, may explain why deer use both secretions . As stated by Ralls (1971) there are at least two possible explanations why mammals scent mark with more than one source of odour in response to one stimulus : the messages sent may be different from each other, or, by sending the same message in different ways, the probability that the message is received is increased . a 2x

4x

75° j

4°/min I b 0 75 0

10

20

4°/min r 10

30

40

min

30

40

min

J 20

Fig . 5 . Gas chromatographs of the contents of antorbital sacs of male black-tailed deer . (a) Yearling (whole contents of one sac from one individual) ; (b) fawns (whole contents of both sacs of two individuals (four sacs)). Note the comparatively small size of the peaks between 25 and 45 min in fawns.

VOLKMAN ET AL . : ANTORBITAL AND FOREHEAD SECRETIONS OF BLACK-TAILED DEER 1105

Rails' explanation is also valid in the case of several stimuli . In black-tailed deer the second explanation is the most probable, that a redundancy of information is created by using both secretions . Other studies have demonstrated the first of Ralls' explanations . Rasa (1973) in her study of the African dwarf mongoose (Helogale), found that anal and cheek gland secretions have different social significances. Anal gland secretions function in recognition of individuals, cheek gland secretions are used as a threat . Mykytowycz (1966) and Goodrich & Mykytowycz (1972) suggested that rabbits (0 . cuniculus) mark their overall territories with the anal gland secretions and with urine, and that localized features are marked with the chin gland. Thiessen & Yahr (1969) noted that in the Mongolian gerbil (Meriones unguiculatus) objects too high to mark with the ventral gland were marked with their chin glands . Several other studies have also examined the roles of multiple sources of olfactory signals including : studies on Meriones by Halpin (1974), Callithrix and Saguinus by Epple (1970, 1971), Canis familiaris by Doty & Dunbar (1974), Antilocapra by Muller-Schwarze, Muller-Schwarze & Franklin (1973), and Lemur catta by Mertl (1975) . In the wild, male black-tailed deer have shared rubbing sites on communal trails and at water holes . Shared and exclusive rubbing sites have been observed in captivity, and the relative number of shared sites increases during the rut (Muller-Schwarze 1972) . These rubbing sites appear to serve as information centres, where deer of both sexes can determine what male deer are within an area, and where male deer can signal their presence. Clearly, knowledge of the age class of male deer is adaptive to all deer . Acknowledgments This study was supported by NSF grant GB26640 to D. Muller-Schwarze . We thank Dr Alf Claesson for performing chemical analyses of antorbital secretions, Dr R . M. Silverstein for critically reading the manuscript, and Ginny Sargent Volkman for advice on computer analyses of our data and for aid in hand-raising fawns . REFERENCES Albone, E. S. & Perry, G. C . 1976 . Anal sac secretions of the red fox, Vulpes vulpes : volatile fatty acids and diamines : implications for a fermentation hypothesis of chemical recognition . J. Chem . Ecol., 2, 101-111 .

Doty, R. L. & Dunbar, I . 1974. Attraction of beagles to conspecific urine, vaginal and anal sac secretion odors. Physiol. and Behav., 12, 825-833. Eisenberg, J. F. & Kleiman, D . G . 1972 . Olfactory communication in mammals . Ann . Rev. Ecol. Syst., 3, 1-32 . Epple, G. 1970 . Quantitative studies on scent marking in the marmoset (Callithrix jacchus) . FoliaPrimatol. (Basel), 13, 48-62. Epple, G . 1971 . Discrimination of the odor of males and females by marmoset Saguinus fuscicollis sp . Proc. 3rd Intern . Congress Primat., 1970. Zurich, Switzerland. 3, 166-171 . Basel, Switzerland : Karger . Goodrich, B. S . & Mykytowycz, R. 1972. Individual and sex differences in the chemical composition of pheromone-like substances from the skin glands of the rabbit, Orcytolagus cuniculus . J. Mammal., 53, 540-548 . Halpin, Z. T. 1974 . Individual differences in the biological odors of the mongolian gerbil (Meriones unguiculatus) . Behav., Biol., 11, 253-259 . Hollander, M . & Wolfe, D . A . 1973 . Nonparametric Statistical Methods. New York : John Wiley and Sons . Mertl, A. S . 1975 . Discrimination of individuals by scent in a primate . Behav. Biol., 14, 505-509. Moore, W. G. & Marchinton, R . L . 1974. Marking behaviour and its function in white-tailed deer . In : The Behaviour of Ungulates and its Relation to Management (Ed. by V. Geist & F . Walther). Morges, Switzerland : IUCN . Muller-Schwarze, D . 1971 . Pheromones in black-tailed deer. Anim . Behav ., 19,141-152. Muller-Schwarze, D . 1972. Social significance of forehead rubbing in black-tailed deer (Odocoileus hemionus columbianus) . Anim . Behav., 20, 788-797 . Muller-Schwarze, D . 1974. Olfactory recognition of species, groups, individuals, and physiological states among mammals . In : Pheromones (Ed . by M . C . Birch), pp . 316-326 . Amsterdam Elsevier Pub . Co. Muller-Schwarze, D . 1975 . A note on the use of the antorbital gland in marking by Eld's deer . Applied Anim. Ethol., 1, 301-303 . Muller-Schwarze, D ., Muller-Schwarze, C. & Franklin, W . L . 1973. Factors influencing scent marking in the pronghorn (Antilocapra americana) . Verhand lurgen der Deutschen Zoologischen Gesellschaft, 66, Jahresversammlung Gustav Fischer Verlag, pp . 146-150. Mykytowycz, R . 1966 . Territorial marking by rabbits . Sci. Amer., 218, 116-126. Quay, W . B . & Muller-Schwarze, D . 1970. Functional histology of integumentary glandular regions in black-tailed deer (Odocoileus hemionus columbianus) . J. Mammal., 51, 675-694. Ralls, K. 1971 . Mammalian scent marking. Science, 171, 442-449 . Rasa, O . A . E . 1973 . Marking behaviour and its social significance in the African dwarf mongoose. Helogale undulata rufula . Z. Tierpsychol., 32, 293-318 .

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Schultze-Westrum, T. G . 1965 . Innerartliche Verstitndigung durch Dtifte beim Gleitbeutler Petaurus breviceps papuanus Thomas (Marsupialia, Phalangeridae). Z. vergl. Pkysiol., 50, 151-220. T. G. 1969. Social communication by chemical signals in flying phalangers (Petaurus breviceps papuanus) . In : Olfaction and Taste (Ed. by C. Pfaffman), pp. 268-277 . New York : Rockefeller University Press .

Thiessen, D . D. & Rice, M . 1976 . Mammalian scent gland marking and social behaviour . Psychol. Bull., 83, 505-539 . Thiessen, D . D . & Yahr, P. 1969. Hormone regulation of ventral marking and chinning in the Mongolian gerbil. Amer. Zool., 9, 1069 . (Received 7 September 1976 ; revised 14 February 1977 ; MS. number :