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Scent-marking behaviour of Meriones hurrianae during oestrus
SHORT COMMUNICATIONS We have not found, in general, that mother rats of either line spend more tinae in the nest with smaller litters, as compared to larger litters. It is paradoxical, however, that the time spent with the litter decreases progressively (also seen between weeks 1 and 2 in the present study for all groups), as the nutritional demands of the pups certainly increase during this time. It has been shown that, since pups in the huddle increase their mass of heat-producing tissue faster than they increase their surface area available for heat loss, maternal temperature rises ever more quickly during nesting bouts over the course of lactation, which serves progressively to curtail the daily nest time (Croskerry et al. 1978). A thermal limitation of nest time may also play a role in the differences seen in this behaviour trait between RHA] Verh and RLA/Verh rats, as the former have on occasion exhibited basal temperatures averaging 0.5 C higher than the latter (Waldvogel 1977; Gentsch, unpublished results). RHA/Verh mothers, which spend less time with their young, also spend more time in the passive nursing position than do RLA/Verh mothers. Whereas this position could theoretically serve as art aid in reducing increases in maternal temperature, other observations have indicated that emotionality or anxiety factors may play a more important role. While attempting to video-tape both nursing positions for educational use, utilizing uncovered cages and strong lighting, we have noted that it was impossible to record the passive nursing position under those conditions, even with RI-IA/Verh litters. Nursing rats may, therefore, assume the active position as a protective posture when induced to do so either by internal (genetic) or external (environmental) stimuli. The authors thank Professor K. B/ittig for his helpful suggestions during the course of this study. H. FUEMM P. DRISCOLL* Institute for Behavioural Science, Swiss Federal Institute of Technology, CH-8092 Ziirich, Switzerland. 9To whom all correspondence should be addressed. References Croskerry, P. G., Smith, G. K. & Leon, M. 1978. Thermoregulation and the maternal behaviour of the rat. Nature, Lond., 273, 299-300. Driscoll, P. & B~ittig, K. 1979. Behavioral and physiological correlates of psychogenetic selection (RHA]Verh vs RLA/Verh rats). In: L'animal de Laboratoire au Service de l'Homme, pp. 477-487. Lyon: Collection Foundation M6rienx. Driscoll, P., Fiimm, H. & B~ittig, K. 1979. Maternal behavior in two rat lines selected for differences in the acquisition of two-way avoidance. Experientia, 35, 786-788. Henning, S. J. & Gisel, E. G. 1980. Nocturnal feeding behavior in the neonatal rat. PhysioL Behav., 25, 603-605. Holland, H. C. 1965. An apparatns note on A.M.B.A. (automatic maternal behaviour apparatus). Anita. Behav., 13, 201-202. Levin, R. & Stern, J. M. 1975. Maternal influences on ontogeny of suckling and feeding rhythms in the rat. J. comp. physiol. PsychoL, 89, 711-721. McIver, A. H. & Jeffrey, W. E. 1967. Strain differences in maternal behavior in rats. Behaviour, 28, 210216.
1269
Waldvogel, R. 1977. Behavioral Thermoregulation. Doctoral dissertation, E. T. H. Ziirich, Nr. 6049, 1-131.
(Received 16 March 1981 ; revised 22 June 1981 ; MS. number: sc-100) Scent-Marking Behaviour of Meriones hurrianae During Oestrus The Indian desert gerbil, Meriones hurrianae (Jerdon) is the most common mammal in the Thar desert. It possesses a well developed ventral scent-marking gland which is larger in the males than in the females (Prakash & Kumari 1979). In nature, M. hurrianae marks the immediate vicinity of the burrow openings and nearby grass clumps (Kumari et al. 1981). The marking behaviour of the Mongolian gerbil, Meriones unguiculatus, has been regarded as having a territorial function (Thiessen 1973), but this does not appear to apply to M. hurrianae, which is categorized as a 'tolerant' rodent (Fitzwater & Prakash 1969). In earlier studies we have also found that the sebum of the mid-ventral gland of the Indian gerbil, Tatera indica, (Kumari & Prakash 1979) and M. hurrianae (unpublished data) has a phagostinmlant property, and it may also have a 'food reservation' function in the latter species since desert gerbils scent-mark vegetation (Kumari & Prakash, 1981) in the desert environment, where there is severe competition for scarce food resources in most years (Prakash 1962). Here we describe the finding that in female M. hurrianae the frequency of scentmarking is increased during oestrus, and consider the possible functional significance of this behaviour. Gerbils were collected from the sandy plains around Jodhpur (26 ~ 18' N-73 ~ 01 'E) and acclimatized to laboratory conditions for two weeks. Ten healthy adult females (body weight 59.1 g :t: 2.99 SE) were then lodged in individual cages and were provided with millet (Pennisetum typhoides) and water ad lib. Stages of the oestrous cycle in these animals were determined by examining vaginal smears, following Allen (1922). In M. hurrianae the vaginal smears show eyelicity only when cycles are ovulatory (Kaul & Ramaswami 1969). The average period of the oestrous cycle in 3,/. hurrianae is 6.2 days (Ghosh & Taneja 1968). The scent-marking behaviour of females both in oestrus and during dioestrus was observed in a glass cage (92•215 cm) for 15 rain daily at 1100 hours. The rodents were provided with metal, glass and plastic objects for marking purposes. The frequencies of marking, urination and defaecation on the wooden floor of the cage and also on objects were recorded. Cages were throughly washed prior to the use of a new animal for observations. The frequency of scent-marking by the female Indian desert gerbils increased significantly (P < 0.01) during pro-oestrus and oestrus in comparison to that during dioestrus (Table I). In all phases marking was carried out significantly more times on objects than on the ground (P < 0.05). Analysis of variance ifidieates that there is a significant difference in the frequency of marking on various objects (Fa6.s = 5.86, P < 0.01). However, no significant difference in the frequency of urination and defaecation was observed between the oestrous and dioestrous phases. In M. hurrianae, there is sexual dimorphism in the size of the ventral scent gland and in marking behaviour. The glands were larger in all males examined (P < 0.001; Prakash & Kumari 1979), and they marked twice as
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SHORT COMMUNICATIONS often as the females (P < 0.01; Kumari et al. 1981). A significant variation (Fll.49 = 3.75, P < 0.05) in the dimensions of the gland between months of the year has been observed in female M. harrianae (unpublished data). There appears to be a correlation between gland dimensions and the two littering periods, the peak breeding season being February to March (spring) and July to September (monsoon; Prakash 1964), This association suggests that the secretory activity of the ventral gland is probably related to reproductive activity. Such a relationship has also been observed in other mammals: European hamster, Cricetus cricetus (Eibl-Eibesfeldt 1953), water vole, Arvicola terrestris (Stoddart 1972), and rabbit, Oryctolagus cuniculus (Mykytowycz 1966). While we have found Indian desert gerbils to mark significantly more frequently during pro-oestrus and oestrus than during dioestrus, no corresponding difference is apparent in the frequency of urination and defaecation between these periods (Table I). The oestrous state may be communicated by olfactory cues from scent-marks and we suggest that the enhanced scent-marking activity of oestrous females may serve to advertise readiness to mate. We are grateful to Dr H. S. Mann, Director, CAZRI, Jodhpur, for encouragement and support, to Dr P. K. Ghosh, Head of the Division of Animal Studies, CAZRI, and to Professor C. J. Dominic, Banaras Hindu University for criticizing the manuscript. SagoJ KtrMam ISHWAR PRAKASH Coordinating and Monitoring Centre for Rodent Research and Training, Central Arid Zone Research Institute, Jodhpur 342 003, India. References Allen, E. t922. The oestrous cycle in the mouse. Am. J. Anat., 30, 297-371. Eibl-Eibesfeldt, I. 1953. Zur Ethologie des Hamsters (Crieetus cricetus). Z. Tierpsychol., 10, 204-254. Fitzwater, W. D. & Prakash, I. 1969. Burrows, behaviour and home range of the Indian desert gerbil, Meriones hurrianae (Jerdon). Mammalia, 33, 598606. Ghosh, P. K. & Taneja, G. C. 1968. Oestrous cycle in the desert rodents, Tatera indica and Meriones hurrianae. Indian& exp. BioL, 6, 54-55. Kaul, D. K. & Ramaswami, L. S. 1969. Reproduction in the Indian desert gerbil, Meriones hurrianae Jerdon. Acta ZooL, 50, 233-248. Kumari, S, & Prakash, I. 1979. Conspecific odour as a phagostimulant for the Indian gerbil, Tatera indica indica Hardwicke. Indian J. exp. BioL, 17, 981-982. Kumari, S. & Prakash, I. 1981. Behavioural responses of Meriones hurrianae (Jerdon) to conspecific sebum odour of ventral sebaceous gland. Biol. Behav, 6, 255-263. Kumari, S., Cowan, P. E. & Prakasb, I. 1981. The mid ventral gland of the Indian desert gerbil, Meriones hurrianae (Jerdon). Acta TherioL, 26, 97-106. Mykytowycz, R. 1966. Observations on odoriferous and other glands in the Australian wild rabbit Oryctolagus cunieulus (L.) and hare Lepus europaeus (P.). CSIRO Wildl. Res., 11, 11-29. Prakash, I. 1962. Ecology of gerbils of the Rajasthan desert, India. Mammalia, 26, 311-331.
1271
Prakash, I. 1964. Eco-toxicology and control of Indian desert gerbil, Meriones hurrianae Jerdon. Part II. Brecxting season, litter size and postnatal development. J. Bombay nat. Hist. Soc., 61, 142-149. Prakash, I. & Kumari, S. 1979. Occurrence of ventral marking gland in desert rodents. Saugt. Mitteil., 27, 315-316. Stoddart, D. M. 1972. The lateral scent organ of Arvicola terrestris (Rodentia: Microtinae). J. Zool., 166, 4%54. Thiessen, D. D. 1973. Foot holds for survival. Am. Scient., 61, 346-351.
(Received 17 March 1981 ; revised 17 June 1981 ; MS. number: sc-106) Experience Leads to Attack of Novel Species By an Interspecific Territorial Damseifish, Eupomacentrus fasciolatus Eupomacentrus fasciolatus, like many herbivorous damselfish, shows selective territorial defence against feeding competitors (Miller 1978). Thresher (1976) suggested that the similar E. planifrons discriminated competitors from non-competitors by their body shape. Classical ethological views of aggression suggest that body shape or other morphological cues might serve as innate releasers (sensu Tinbergen 1951) for aggression. However, the diverse morphology of coral reef herbivores presents a prodigious challenge for complete genetic coding for all competitors. A parallel or even alternative hypothesis tested here is that selection has favoured response to ecological cues that characterize competitors, such as their method of feeding. Such cues might release aggressive responses or serve as experiential cues leading to the development of an aggressive response to that species. Dependence on ecological cues should result in desirable flexibility of interspecific response in different habitats and faunas. Territory holders could learn which members of ecologically diverse but morphologically conservative families (e.g. Chaetodontidae) posed a competitive threat. The hypothesis that competitor discrimination can be affected by experience was tested by exposing damselfish to a novel opponent trained to feed like an herbivore but with the morphological characters of a predator. Two adult E. fasciolatus were placed in 11 to 12 m s concrete ponds with five to seven other herbivorous fish (Aeanthurus triostegus, Zebrasoma flavescens and Scarus spp.) and usually one non-competitor (Thalassoma duperry). Five individuals from the first four pairs of damselfish formed territories and are reported on here. An observer over the tank collected the following data on a grid pattern with one-foot-square cells: A, attacks by the damsel as the number of chases plus 0.5 times the number of approaches per cell; L 'intrusion' by each species of competitor on a 5-s 'one-zero' sampling schedule as the number of feeds plus 0.5 times the number of samples with the fish within two body lengths of the bottom plus 0.3 times the number of samples when greater than two body lengths from the bottom. Territory borders were defined as a simple geometric shape including the defended algal mat. The territory core was defined as all ceils except the border cells. After the feeding ranges and attacking stabilized, behavioural observations were taken. An individual Sarotherodon mossambica (tilapia), a euryhaline fish not found on Hawaiian reefs, was then added and observations were repeated. Bricks smeared with an agar mixture of 'fish fudge' which the tilapia had been trained to feed on were then placed adjacent to and just inside of the
1269
Waldvogel, R. 1977. Behavioral Thermoregulation. Doctoral dissertation, E. T. H. Ziirich, Nr. 6049, 1-131.
(Received 16 March 1981 ; revised 22 June 1981 ; MS. number: sc-100) Scent-Marking Behaviour of Meriones hurrianae During Oestrus The Indian desert gerbil, Meriones hurrianae (Jerdon) is the most common mammal in the Thar desert. It possesses a well developed ventral scent-marking gland which is larger in the males than in the females (Prakash & Kumari 1979). In nature, M. hurrianae marks the immediate vicinity of the burrow openings and nearby grass clumps (Kumari et al. 1981). The marking behaviour of the Mongolian gerbil, Meriones unguiculatus, has been regarded as having a territorial function (Thiessen 1973), but this does not appear to apply to M. hurrianae, which is categorized as a 'tolerant' rodent (Fitzwater & Prakash 1969). In earlier studies we have also found that the sebum of the mid-ventral gland of the Indian gerbil, Tatera indica, (Kumari & Prakash 1979) and M. hurrianae (unpublished data) has a phagostinmlant property, and it may also have a 'food reservation' function in the latter species since desert gerbils scent-mark vegetation (Kumari & Prakash, 1981) in the desert environment, where there is severe competition for scarce food resources in most years (Prakash 1962). Here we describe the finding that in female M. hurrianae the frequency of scentmarking is increased during oestrus, and consider the possible functional significance of this behaviour. Gerbils were collected from the sandy plains around Jodhpur (26 ~ 18' N-73 ~ 01 'E) and acclimatized to laboratory conditions for two weeks. Ten healthy adult females (body weight 59.1 g :t: 2.99 SE) were then lodged in individual cages and were provided with millet (Pennisetum typhoides) and water ad lib. Stages of the oestrous cycle in these animals were determined by examining vaginal smears, following Allen (1922). In M. hurrianae the vaginal smears show eyelicity only when cycles are ovulatory (Kaul & Ramaswami 1969). The average period of the oestrous cycle in 3,/. hurrianae is 6.2 days (Ghosh & Taneja 1968). The scent-marking behaviour of females both in oestrus and during dioestrus was observed in a glass cage (92•215 cm) for 15 rain daily at 1100 hours. The rodents were provided with metal, glass and plastic objects for marking purposes. The frequencies of marking, urination and defaecation on the wooden floor of the cage and also on objects were recorded. Cages were throughly washed prior to the use of a new animal for observations. The frequency of scent-marking by the female Indian desert gerbils increased significantly (P < 0.01) during pro-oestrus and oestrus in comparison to that during dioestrus (Table I). In all phases marking was carried out significantly more times on objects than on the ground (P < 0.05). Analysis of variance ifidieates that there is a significant difference in the frequency of marking on various objects (Fa6.s = 5.86, P < 0.01). However, no significant difference in the frequency of urination and defaecation was observed between the oestrous and dioestrous phases. In M. hurrianae, there is sexual dimorphism in the size of the ventral scent gland and in marking behaviour. The glands were larger in all males examined (P < 0.001; Prakash & Kumari 1979), and they marked twice as
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SHORT COMMUNICATIONS often as the females (P < 0.01; Kumari et al. 1981). A significant variation (Fll.49 = 3.75, P < 0.05) in the dimensions of the gland between months of the year has been observed in female M. harrianae (unpublished data). There appears to be a correlation between gland dimensions and the two littering periods, the peak breeding season being February to March (spring) and July to September (monsoon; Prakash 1964), This association suggests that the secretory activity of the ventral gland is probably related to reproductive activity. Such a relationship has also been observed in other mammals: European hamster, Cricetus cricetus (Eibl-Eibesfeldt 1953), water vole, Arvicola terrestris (Stoddart 1972), and rabbit, Oryctolagus cuniculus (Mykytowycz 1966). While we have found Indian desert gerbils to mark significantly more frequently during pro-oestrus and oestrus than during dioestrus, no corresponding difference is apparent in the frequency of urination and defaecation between these periods (Table I). The oestrous state may be communicated by olfactory cues from scent-marks and we suggest that the enhanced scent-marking activity of oestrous females may serve to advertise readiness to mate. We are grateful to Dr H. S. Mann, Director, CAZRI, Jodhpur, for encouragement and support, to Dr P. K. Ghosh, Head of the Division of Animal Studies, CAZRI, and to Professor C. J. Dominic, Banaras Hindu University for criticizing the manuscript. SagoJ KtrMam ISHWAR PRAKASH Coordinating and Monitoring Centre for Rodent Research and Training, Central Arid Zone Research Institute, Jodhpur 342 003, India. References Allen, E. t922. The oestrous cycle in the mouse. Am. J. Anat., 30, 297-371. Eibl-Eibesfeldt, I. 1953. Zur Ethologie des Hamsters (Crieetus cricetus). Z. Tierpsychol., 10, 204-254. Fitzwater, W. D. & Prakash, I. 1969. Burrows, behaviour and home range of the Indian desert gerbil, Meriones hurrianae (Jerdon). Mammalia, 33, 598606. Ghosh, P. K. & Taneja, G. C. 1968. Oestrous cycle in the desert rodents, Tatera indica and Meriones hurrianae. Indian& exp. BioL, 6, 54-55. Kaul, D. K. & Ramaswami, L. S. 1969. Reproduction in the Indian desert gerbil, Meriones hurrianae Jerdon. Acta ZooL, 50, 233-248. Kumari, S, & Prakash, I. 1979. Conspecific odour as a phagostimulant for the Indian gerbil, Tatera indica indica Hardwicke. Indian J. exp. BioL, 17, 981-982. Kumari, S. & Prakash, I. 1981. Behavioural responses of Meriones hurrianae (Jerdon) to conspecific sebum odour of ventral sebaceous gland. Biol. Behav, 6, 255-263. Kumari, S., Cowan, P. E. & Prakasb, I. 1981. The mid ventral gland of the Indian desert gerbil, Meriones hurrianae (Jerdon). Acta TherioL, 26, 97-106. Mykytowycz, R. 1966. Observations on odoriferous and other glands in the Australian wild rabbit Oryctolagus cunieulus (L.) and hare Lepus europaeus (P.). CSIRO Wildl. Res., 11, 11-29. Prakash, I. 1962. Ecology of gerbils of the Rajasthan desert, India. Mammalia, 26, 311-331.
1271
Prakash, I. 1964. Eco-toxicology and control of Indian desert gerbil, Meriones hurrianae Jerdon. Part II. Brecxting season, litter size and postnatal development. J. Bombay nat. Hist. Soc., 61, 142-149. Prakash, I. & Kumari, S. 1979. Occurrence of ventral marking gland in desert rodents. Saugt. Mitteil., 27, 315-316. Stoddart, D. M. 1972. The lateral scent organ of Arvicola terrestris (Rodentia: Microtinae). J. Zool., 166, 4%54. Thiessen, D. D. 1973. Foot holds for survival. Am. Scient., 61, 346-351.
(Received 17 March 1981 ; revised 17 June 1981 ; MS. number: sc-106) Experience Leads to Attack of Novel Species By an Interspecific Territorial Damseifish, Eupomacentrus fasciolatus Eupomacentrus fasciolatus, like many herbivorous damselfish, shows selective territorial defence against feeding competitors (Miller 1978). Thresher (1976) suggested that the similar E. planifrons discriminated competitors from non-competitors by their body shape. Classical ethological views of aggression suggest that body shape or other morphological cues might serve as innate releasers (sensu Tinbergen 1951) for aggression. However, the diverse morphology of coral reef herbivores presents a prodigious challenge for complete genetic coding for all competitors. A parallel or even alternative hypothesis tested here is that selection has favoured response to ecological cues that characterize competitors, such as their method of feeding. Such cues might release aggressive responses or serve as experiential cues leading to the development of an aggressive response to that species. Dependence on ecological cues should result in desirable flexibility of interspecific response in different habitats and faunas. Territory holders could learn which members of ecologically diverse but morphologically conservative families (e.g. Chaetodontidae) posed a competitive threat. The hypothesis that competitor discrimination can be affected by experience was tested by exposing damselfish to a novel opponent trained to feed like an herbivore but with the morphological characters of a predator. Two adult E. fasciolatus were placed in 11 to 12 m s concrete ponds with five to seven other herbivorous fish (Aeanthurus triostegus, Zebrasoma flavescens and Scarus spp.) and usually one non-competitor (Thalassoma duperry). Five individuals from the first four pairs of damselfish formed territories and are reported on here. An observer over the tank collected the following data on a grid pattern with one-foot-square cells: A, attacks by the damsel as the number of chases plus 0.5 times the number of approaches per cell; L 'intrusion' by each species of competitor on a 5-s 'one-zero' sampling schedule as the number of feeds plus 0.5 times the number of samples with the fish within two body lengths of the bottom plus 0.3 times the number of samples when greater than two body lengths from the bottom. Territory borders were defined as a simple geometric shape including the defended algal mat. The territory core was defined as all ceils except the border cells. After the feeding ranges and attacking stabilized, behavioural observations were taken. An individual Sarotherodon mossambica (tilapia), a euryhaline fish not found on Hawaiian reefs, was then added and observations were repeated. Bricks smeared with an agar mixture of 'fish fudge' which the tilapia had been trained to feed on were then placed adjacent to and just inside of the