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Determination of the causes of infanticide in capybara (Hydrochaeris hydrochaeris) groups in captivity
Applied Animal Behaviour Science 62 Ž1999. 351–357
Determination of the causes of infanticide in capybara žHydrochaeris hydrochaeris / groups in captivity Selene Siqueira da Cunha Nogueira ) , Sergio Luiz Gama ´ Nogueira-Filho, Emma Otta, Carlos Tadeu dos Santos Dias, Alessandra de Carvalho Departamento de Zootecniar ESALQr UniÕersidade de Sao ˜ Paulo, C.P. 9, Piracicaba-SP CEP: 13418900 Brazil Accepted 16 October 1998
Abstract The capybara Ž Hydrochaeris hydrochaeris. is a wild rodent of great economical interest, which are easily domesticated. Breeding these animals in captivity constitutes a great problem due to the high rate of offspring mortality caused by infanticide. To determine the causes of the infanticides, 64 capybara births were analyzed in order to study the relation of offspring deaths with the lack experience of primiparous females, place of parturition–maternity pen Žisolated. vs. reproduction pen Žin-group. or familiarity among group members. The hypothesis that primiparous females kill their own offspring was discarded. The data revealed that the infanticides were associated with reproductive groups containing females who have not been together since weaning Žunfamiliar females. in spite of living together without apparent conflicts until the occurrence of births, when they killed the companions’ offspring. This study revealed that when groups are set up of females that were living together since weaning, there is no need to isolate the females for parturition. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Capybara; Infanticide; Familiarity; Social behavior; Captivity
1. Introduction The capybara Ž Hydrochaeris hydrochaeris. is a rodent of great interest for animal production, due to its high reproductive rate and herbivorous diet which results in low )
Corresponding author. Fax: q55-19-4294285; e-mail: [email protected]
0168-1591r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 1 5 9 1 Ž 9 8 . 0 0 2 3 1 - 7
352
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
production costs. The consumption of capybara meat in Venezuela and Brazil is a cultural custom and the commercial production of this species has grown as a production alternative in marginal areas of rural properties ŽLopez-Barbella, 1984; FAO, 1987; ´ Gonzalez-Jimenez, 1995; Nogueira-Filho et al., 1996; Moreira and Macdonald, 1997.. ´ ´ Breeding these animals in captivity constitutes a great problem due to the high rate of offspring mortality caused by infanticide. In the Escola Superior de Agricultura ‘Luiz de Queiroz’ of the University of Sao ˜ Paulo ŽESALQrUSP., the offspring’s mortality rate was 27.57% due to infanticide ŽNogueira-Filho et al., submitted.. A solution for this problem was to isolate pregnant females for parturition, as in nature, where a female separates from the rest of the group to give birth ŽOjasti, 1973; Fuerbringer, 1974.. This ¨ practice resulted in high costs of facilities and problems at the time of reintroduction of the isolated female to the original group. These females were treated as strange individuals by the group, being attacked and wounded. Those females were removed from the reproduction pen to avoid deaths, which resulted in several females without groups. We studied the possibility of creating new reproduction groups of those individuals and verified that the initial aggressiveness disappeared in a short time and the females started to live together without serious conflicts in the reproduction pens. In some cases, due to the failure to predict the time of the birth, females ended up giving birth within the group. The outcome of this parturition varied. In some groups, the offspring was well accepted by the male and other females and usually grew in the reproduction pen. In other groups, the other females did not accept the new members and killed them. The observation that females could give birth in the group without the occurrence of infanticides suggested the importance of analyzing the need to isolate the capybaras for the birth and of studying the causes of infanticides in the reproduction pens. The occurrence of infanticide among individuals of the same group seems strange in the capybara society where the nursing of non-offspring is verified ŽMacdonald, 1981. and where the young are protected by other females of the group Ž‘aunts’. ŽOjasti, 1973; Macdonald, 1981; Schaller and Crawshaw, 1981; Lord, 1994.. To determine the causes of the infanticides in ESALQrUSP, we tested if the frequency of infanticide was higher among females lacking previous experience, in comparison with multiparous females. We evaluated also if the place of parturition– maternity pen Žisolated. vs. reproduction pen Žin-group. —influenced the infanticides or if there were any relations between infanticides and familiarity among the individuals of the reproduction groups.
2. Materials and methods 2.1. Animals We analyzed 64 capybara births recorded in ESALQrUSP from 1984 to 1995. Of these births, 25 took place in maternity pens in which the females were isolated for the parturition and 39 in reproduction pens, where females gave birth in the middle of the group.
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
353
2.2. Equipment Reproduction pen: in these pens there were groups of one male and five to seven females in an area of 120 m2 , comprising a sheltered area Ž22 m2 ., and a unsheltered area or exercise area Ž98 m2 .. The covered area was used to protect the animals from the rain and sun. In the exercise area there was a water tank of 3.0 m = 2.0 m and 1.0 m of depth. Maternity pen: this space was used to isolate females approaching the parturition. It measured 12 m2 , with a water tank of 1 m2 , covered area with 4 m2 and the remainder was part of the exercise area ŽAndrade, 1996.. 2.3. Methods We collected data from all births recorded during this period, separating the females in two groups: Ža. those that gave birth in maternity pens Žisolated. and Žb. the ones that gave birth within the reproduction pens Žin-group.. After allocating females to each group, we created two subgroups, composed of primiparous females and multiparous females and recorded the number of infanticides in each situation. We considered infanticides the killing of one or more youngs by the mother or other female of the group, since the deaths were never caused by males in ESALQrUSP ŽLavorenti, personal communication.. From the total females giving birth in reproduction pens, we selected 14 groups where familiarity among females that shared the same pen was known. Familiarity was defined as having grown in the same pen since weaning, which happen at around 2 months of age. Two types of reproduction groups were formed: Ža. composed of females who have not been together since weaning Žunfamiliar females. Ž N s 8.; Žb. composed of familiarized females, that is, which had lived together in the same pen at least since weaning Ž N s 6.. The data were analyzed through the chi-square test Ž x 2 . of Mantel–Haenszel with one degree of freedom. That test is specific for survival data. The analysis were made
Table 1 Frequency of infanticides considering the females’ experience: primiparous vs. multiparous females isolated in maternity pens and reproduction pens Žexpected frequencies in parenthesis. Female category
Infanticides
a. Maternity pens Primiparous Multiparous Total b. Reproduction pens Primiparous Multiparous Total
No infanticides
Total
0 Ž0.96. 2 Ž1.04. 2
12 Ž11.04. 11 Ž11.96. 23
12 13 25
13 Ž12.46. 5 Ž5.54. 18
14 Ž14.54. 7 Ž6.46. 21
27 12 39
354
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
Table 2 Frequency of infanticides considering the parturition place Žexpected frequencies in parenthesis. Parturition place
Infanticides
No infanticides
Total
Maternity pen Žisolated. Reproduction pen Žin-group. Total
2 Ž7.81. 18 Ž12.18. 20
23 Ž17.18. 21 Ž26.81. 44
25 39 64
through the software STATISTICAL ANALISYS SYSTEM ŽHEALTHY. —version 6.08.
3. Results 3.1. Infanticide considering the experience of the females (primiparous or multiparous) in maternity and reproduction pens We verified that the rate of infanticides was the same for primiparous and multiparous females. For the females isolated in the maternity pens ŽTable 1a. Ž x 2 s 1.926; df s 1; p ) 0.05, Mantel–Haenszel., the same was true for the ones that gave birth in reproduction pens Ž x 2 s 0.137; df s 1; p ) 0.05, Mantel–Haenszel. ŽTable 1b.. 3.2. Infanticide considering the place of the parturition (maternity pen or reproduction pen) The infanticide rate was significantly higher when the females gave birth in the reproduction groups than in the case of the females isolated in maternity pens Ž x 2 s 10.161; df s 1; p - 0.05, Mantel–Haenszel. ŽTable 2.. 3.3. Infanticide in function of the familiarity We verified that infanticides took place only in groups in which females were unfamiliar with each other, in the sense defined above. Ž x 2 s 20.329; df s 1; p - 0.01, Mantel–Haenszel. ŽTable 3..
Table 3 Frequency of infanticides of the familiar and unfamiliar groups Žexpected frequencies in parenthesis. Groups
Infanticides
No infanticides
Total
Familiar females Unfamiliar females Total
0 Ž7.35. 24 Ž16.65. 24
15 Ž7.65. 10 Ž17.35. 25
15 34 49
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
355
4. Discussion Under natural conditions, the capybara females separate spontaneously from the group some hours before giving birth. They look for shelter under bushes or make a nest among the grass ŽOjasti, 1973.. When giving birth, the female immediately cleans and removes the placenta residues of the offspring by licking and biting. This cleaning begins at the head and continues down to the abdominal area and legs. This is a delicate process, which takes seconds, when the mother must control the force of the bites so as not to mutilate the newborn. The stress of the female on this occasion can endanger the whole litter. The female eats all the placenta after each birth, leaving the birthplace practically clean of vestiges ŽNogueira-Filho, personal observation.. Only several days after giving birth does the mother return to the group with her offspring ŽOjasti, 1973; Lopez-Barbella, 1984.. ´ The isolation of the capybara female in nature can be related with the difficulties of locomotion at the moment of birth, as what happens in sheep ŽPoindron et al., 1994.. This behavior may be due to the blood lost by the females, which would attract predators that could attack the whole group if she were close to it. It is more difficult for Ž1974. suggested the predator to find the isolated female. On the other hand, Fuerbringer ¨ that females stand alone to give birth in order to defend their offspring from the males: ‘‘ . . . old and neurotic males that eliminate them in purpose of limiting the surpluses of the flock.’’ In light of our findings, this observation seems to be a misinterpretation common among rural producers when they come across dead offspring and see a male close by. In fact, a protecting posture of the male in relation to the offspring was observed several times ŽNogueira et al., submitted.. The deaths could result from lack of experience of the females who do not know how to measure the intensity of the force in cleaning the offspring or for not defending them at the introduction of these to the other members of the group. No studies exist regarding the establishment of relationship between the female and her offspring, or if the females learn from the experience of the first parturition, to be more successful in the subsequent ones. In Mus musculus and sheep, studies suggest that the experience acquired with the previous births is important for the maternal success ŽSalmon, 1987; Levy ´ et al., 1995.. However, the results of the present study showed that capybara females did not kill their offspring due to lack of experience: both primiparous and multiparous females presented the same rate of offspring mortality. This study indicates that the birthplace was related to the infanticides. In maternity pens, there were significantly less infanticides than in reproduction pens. Perhaps the few infanticides in the isolation pens were related with the stress of the confined females, because of handling and transport for pen, due to the short time for adaptation to the new environment or the presence of strange animals in the neighboring pens that may have displayed aggressiveness. This fact corroborates the suggestion of Salmon Ž1987. in M. musculus, for which stress of the pregnant females can cause the infanticide of the newborn. In a peaceful place, the mother is more efficient in the care of the newborn, which elevates the reproductive success. Most of the infanticides were registered in reproduction pens containing animals that were not familiar. Either the females killed each other’s offspring or the mothers
356
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
themselves could have killed their young in the moment of the cleaning, due to stress. If they feel in danger, there may be a risk of biting the offspring at this moment, causing deaths. We verified that in spite of the apparent harmonic conviviality among the females of the groups formed with adult animals, intolerance exists to the newborn. These facts suggest that the familiarity among the females should be taken into account for formation of reproduction groups, in order to eliminate the isolation for parturition. The present study suggests that in intensive breeding, the capybara females do not need isolation pens to give birth, as long as reproduction groups live together since weaning and no member removed and then reintroduced. In this way, expenses of building maternity pens and handling pregnant females can be cut down. This may also enable the reduction of interbirth intervals because they have ovulation during lactation ŽNogueira-Filho et al., submitted.. Also, both stresses during birth and possible rejection by groups after isolation can be reduced. Nevertheless, when there are animals of different origins living together in the same pen, the isolation is essential to avoid the occurrence of infanticides. This same rule is valid when reproduction of capybaras in semi-intensive system on larger areas is intended. In two commercial farms that we visited, infanticides were recorded after the introduction of unfamiliar individuals to the resident groups ŽFossalussa and Nespolo, personal communication..
Acknowledgements We are grateful to Dr. J. Ojasti for making many helpful suggestions and critically reviewing the manuscript. For Denise Rossi and Sabine Pompeia we thank the manuscript translate reviewed. The work was supported by a postgraduate grant to SSCN from CNPq ŽBrazil..
References Andrade, P., 1996. Nıveis de proteına ´ ´ e energia em rac¸oes ˜ e manejo de capivaras Ž Hydrochoerus hydrochaeris hydrochaeris L. 1766. em crescimento. MS Thesis, Universidade de Sao ˜ Paulo, Piracicaba, Brasil, 160 pp. FAO, 1987. Informe del taller sobre las estrategicas para el manejo y el aprovechamiento racional de ´ capybaras, cayman y tortugas de agua dulce ŽSao ˜ Paulo, Brasil. Santiago: Oficina Regional de la FAO para Am. Latina y el Caribe, Santiago, Chile, 50 pp. Fuerbringer, J., 1974. El chiguiro, su crıa ¨ ¨ ´ y exploracion ´ racional. Orientacion ´ Agropecuaria, Bogota, ´ Colombia, 99, pp. 5–59. Gonzalez-Jimenez, E., 1995. El capybara Ž Hydrochoerus hydrochaeris.: estado actual de su produccion. ´ ´ ´ FAO ŽSerie Estudio FAO, Produccion y Sanidad Animal, 122, Roma, 110 pp. Levy, F., Locatelli, A., Piketty, V., Tillet, Y., Poindron, P., 1995. Involvement of the main but not the ´ accessory olfactory system in maternal behavior of primıparous and multiparous ewes. Physiology and ´ Behavior 57, 97–104. Lopez-Barbella, S., 1984. Una contribuicion al conocimento de la reproduccion del chiguire ´ ¨ Ž Hydrochoerus hydrochaeris.. Informe Anual do IPA, pp. 109–117. Lord, R.D., 1994. A descriptive account of capybara behaviour. Studies on Neotropical Fauna and Environment 29, 11–22. Macdonald, D.W., 1981. Dwindling resources and the social behavior of capybara Ž Hydrochoerus hydrochaeris . ŽMammalia.. Journal of Zoology of London 194, 371–391.
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Moreira, J.R., Macdonald, D.W., 1997. Tecnicas de manejo de capivaras e outros grandes roedores na ´ Amazonia. In: C. Valladares-Padua, R.E. Bodmer, L. Cullen, Jr. ŽEds.., Manejo e Conservac¸ao ˆ ˜ de Vida Silvestre no Brasil, Brasılia, ´ D.F., CNPqrBelem, ´ PA: Sociedade Civil Mamiraua, ´ 296 pp. Nogueira, S.S.C., Nogueira-Filho, S.L.G., Dias, C.T.S., submitted. Alloparental behavior in capybara Ž Hydrochaeris hydrochaeris.. Behavioral Ecology and Sociobiology. Nogueira-Filho, S.L.G., Nogueira, S.S.C., Nogueira, M., 1996. Criac¸ao ˜ de capivaras. ed. CPT, Vic¸osa, Brasil, 50 pp. Nogueira-Filho, S.L.G., Nogueira, S.S.C., Dias, C.T.S. Žsubmitted.. Reproductive parameters of capybara Ž Hydrochaeris hydrochaeris. in captivity. Anim. Rep. Sci. Ojasti, J., 1973. Estudio del chiguire ¨ o capybara. Fondo Nacional de Investigaciones Agropecuarias-Caracas, 275 pp. Poindron, P., Caba, M., Arrati, P.G., Krehbiel, D., Beyer, C., 1994. Responses of maternal and non-maternal ewes to social and mother-young separation. Behavioral Process 31 Ž1., 97–110. Salmon, C.C., 1987. Differences in patterns of pup care in Mus musculus domesticus: VIII. Effects of previous experience and parity in XLII inbred mice. Physiology and Behavior 40, 177–180. Schaller, G.B., Crawshaw, P. Jr., 1981. Social organization in a capybara population. Saugetierkundliche, ¨ Mitteilungen 29, 3–16.
Determination of the causes of infanticide in capybara žHydrochaeris hydrochaeris / groups in captivity Selene Siqueira da Cunha Nogueira ) , Sergio Luiz Gama ´ Nogueira-Filho, Emma Otta, Carlos Tadeu dos Santos Dias, Alessandra de Carvalho Departamento de Zootecniar ESALQr UniÕersidade de Sao ˜ Paulo, C.P. 9, Piracicaba-SP CEP: 13418900 Brazil Accepted 16 October 1998
Abstract The capybara Ž Hydrochaeris hydrochaeris. is a wild rodent of great economical interest, which are easily domesticated. Breeding these animals in captivity constitutes a great problem due to the high rate of offspring mortality caused by infanticide. To determine the causes of the infanticides, 64 capybara births were analyzed in order to study the relation of offspring deaths with the lack experience of primiparous females, place of parturition–maternity pen Žisolated. vs. reproduction pen Žin-group. or familiarity among group members. The hypothesis that primiparous females kill their own offspring was discarded. The data revealed that the infanticides were associated with reproductive groups containing females who have not been together since weaning Žunfamiliar females. in spite of living together without apparent conflicts until the occurrence of births, when they killed the companions’ offspring. This study revealed that when groups are set up of females that were living together since weaning, there is no need to isolate the females for parturition. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Capybara; Infanticide; Familiarity; Social behavior; Captivity
1. Introduction The capybara Ž Hydrochaeris hydrochaeris. is a rodent of great interest for animal production, due to its high reproductive rate and herbivorous diet which results in low )
Corresponding author. Fax: q55-19-4294285; e-mail: [email protected]
0168-1591r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 1 5 9 1 Ž 9 8 . 0 0 2 3 1 - 7
352
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
production costs. The consumption of capybara meat in Venezuela and Brazil is a cultural custom and the commercial production of this species has grown as a production alternative in marginal areas of rural properties ŽLopez-Barbella, 1984; FAO, 1987; ´ Gonzalez-Jimenez, 1995; Nogueira-Filho et al., 1996; Moreira and Macdonald, 1997.. ´ ´ Breeding these animals in captivity constitutes a great problem due to the high rate of offspring mortality caused by infanticide. In the Escola Superior de Agricultura ‘Luiz de Queiroz’ of the University of Sao ˜ Paulo ŽESALQrUSP., the offspring’s mortality rate was 27.57% due to infanticide ŽNogueira-Filho et al., submitted.. A solution for this problem was to isolate pregnant females for parturition, as in nature, where a female separates from the rest of the group to give birth ŽOjasti, 1973; Fuerbringer, 1974.. This ¨ practice resulted in high costs of facilities and problems at the time of reintroduction of the isolated female to the original group. These females were treated as strange individuals by the group, being attacked and wounded. Those females were removed from the reproduction pen to avoid deaths, which resulted in several females without groups. We studied the possibility of creating new reproduction groups of those individuals and verified that the initial aggressiveness disappeared in a short time and the females started to live together without serious conflicts in the reproduction pens. In some cases, due to the failure to predict the time of the birth, females ended up giving birth within the group. The outcome of this parturition varied. In some groups, the offspring was well accepted by the male and other females and usually grew in the reproduction pen. In other groups, the other females did not accept the new members and killed them. The observation that females could give birth in the group without the occurrence of infanticides suggested the importance of analyzing the need to isolate the capybaras for the birth and of studying the causes of infanticides in the reproduction pens. The occurrence of infanticide among individuals of the same group seems strange in the capybara society where the nursing of non-offspring is verified ŽMacdonald, 1981. and where the young are protected by other females of the group Ž‘aunts’. ŽOjasti, 1973; Macdonald, 1981; Schaller and Crawshaw, 1981; Lord, 1994.. To determine the causes of the infanticides in ESALQrUSP, we tested if the frequency of infanticide was higher among females lacking previous experience, in comparison with multiparous females. We evaluated also if the place of parturition– maternity pen Žisolated. vs. reproduction pen Žin-group. —influenced the infanticides or if there were any relations between infanticides and familiarity among the individuals of the reproduction groups.
2. Materials and methods 2.1. Animals We analyzed 64 capybara births recorded in ESALQrUSP from 1984 to 1995. Of these births, 25 took place in maternity pens in which the females were isolated for the parturition and 39 in reproduction pens, where females gave birth in the middle of the group.
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
353
2.2. Equipment Reproduction pen: in these pens there were groups of one male and five to seven females in an area of 120 m2 , comprising a sheltered area Ž22 m2 ., and a unsheltered area or exercise area Ž98 m2 .. The covered area was used to protect the animals from the rain and sun. In the exercise area there was a water tank of 3.0 m = 2.0 m and 1.0 m of depth. Maternity pen: this space was used to isolate females approaching the parturition. It measured 12 m2 , with a water tank of 1 m2 , covered area with 4 m2 and the remainder was part of the exercise area ŽAndrade, 1996.. 2.3. Methods We collected data from all births recorded during this period, separating the females in two groups: Ža. those that gave birth in maternity pens Žisolated. and Žb. the ones that gave birth within the reproduction pens Žin-group.. After allocating females to each group, we created two subgroups, composed of primiparous females and multiparous females and recorded the number of infanticides in each situation. We considered infanticides the killing of one or more youngs by the mother or other female of the group, since the deaths were never caused by males in ESALQrUSP ŽLavorenti, personal communication.. From the total females giving birth in reproduction pens, we selected 14 groups where familiarity among females that shared the same pen was known. Familiarity was defined as having grown in the same pen since weaning, which happen at around 2 months of age. Two types of reproduction groups were formed: Ža. composed of females who have not been together since weaning Žunfamiliar females. Ž N s 8.; Žb. composed of familiarized females, that is, which had lived together in the same pen at least since weaning Ž N s 6.. The data were analyzed through the chi-square test Ž x 2 . of Mantel–Haenszel with one degree of freedom. That test is specific for survival data. The analysis were made
Table 1 Frequency of infanticides considering the females’ experience: primiparous vs. multiparous females isolated in maternity pens and reproduction pens Žexpected frequencies in parenthesis. Female category
Infanticides
a. Maternity pens Primiparous Multiparous Total b. Reproduction pens Primiparous Multiparous Total
No infanticides
Total
0 Ž0.96. 2 Ž1.04. 2
12 Ž11.04. 11 Ž11.96. 23
12 13 25
13 Ž12.46. 5 Ž5.54. 18
14 Ž14.54. 7 Ž6.46. 21
27 12 39
354
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
Table 2 Frequency of infanticides considering the parturition place Žexpected frequencies in parenthesis. Parturition place
Infanticides
No infanticides
Total
Maternity pen Žisolated. Reproduction pen Žin-group. Total
2 Ž7.81. 18 Ž12.18. 20
23 Ž17.18. 21 Ž26.81. 44
25 39 64
through the software STATISTICAL ANALISYS SYSTEM ŽHEALTHY. —version 6.08.
3. Results 3.1. Infanticide considering the experience of the females (primiparous or multiparous) in maternity and reproduction pens We verified that the rate of infanticides was the same for primiparous and multiparous females. For the females isolated in the maternity pens ŽTable 1a. Ž x 2 s 1.926; df s 1; p ) 0.05, Mantel–Haenszel., the same was true for the ones that gave birth in reproduction pens Ž x 2 s 0.137; df s 1; p ) 0.05, Mantel–Haenszel. ŽTable 1b.. 3.2. Infanticide considering the place of the parturition (maternity pen or reproduction pen) The infanticide rate was significantly higher when the females gave birth in the reproduction groups than in the case of the females isolated in maternity pens Ž x 2 s 10.161; df s 1; p - 0.05, Mantel–Haenszel. ŽTable 2.. 3.3. Infanticide in function of the familiarity We verified that infanticides took place only in groups in which females were unfamiliar with each other, in the sense defined above. Ž x 2 s 20.329; df s 1; p - 0.01, Mantel–Haenszel. ŽTable 3..
Table 3 Frequency of infanticides of the familiar and unfamiliar groups Žexpected frequencies in parenthesis. Groups
Infanticides
No infanticides
Total
Familiar females Unfamiliar females Total
0 Ž7.35. 24 Ž16.65. 24
15 Ž7.65. 10 Ž17.35. 25
15 34 49
S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
355
4. Discussion Under natural conditions, the capybara females separate spontaneously from the group some hours before giving birth. They look for shelter under bushes or make a nest among the grass ŽOjasti, 1973.. When giving birth, the female immediately cleans and removes the placenta residues of the offspring by licking and biting. This cleaning begins at the head and continues down to the abdominal area and legs. This is a delicate process, which takes seconds, when the mother must control the force of the bites so as not to mutilate the newborn. The stress of the female on this occasion can endanger the whole litter. The female eats all the placenta after each birth, leaving the birthplace practically clean of vestiges ŽNogueira-Filho, personal observation.. Only several days after giving birth does the mother return to the group with her offspring ŽOjasti, 1973; Lopez-Barbella, 1984.. ´ The isolation of the capybara female in nature can be related with the difficulties of locomotion at the moment of birth, as what happens in sheep ŽPoindron et al., 1994.. This behavior may be due to the blood lost by the females, which would attract predators that could attack the whole group if she were close to it. It is more difficult for Ž1974. suggested the predator to find the isolated female. On the other hand, Fuerbringer ¨ that females stand alone to give birth in order to defend their offspring from the males: ‘‘ . . . old and neurotic males that eliminate them in purpose of limiting the surpluses of the flock.’’ In light of our findings, this observation seems to be a misinterpretation common among rural producers when they come across dead offspring and see a male close by. In fact, a protecting posture of the male in relation to the offspring was observed several times ŽNogueira et al., submitted.. The deaths could result from lack of experience of the females who do not know how to measure the intensity of the force in cleaning the offspring or for not defending them at the introduction of these to the other members of the group. No studies exist regarding the establishment of relationship between the female and her offspring, or if the females learn from the experience of the first parturition, to be more successful in the subsequent ones. In Mus musculus and sheep, studies suggest that the experience acquired with the previous births is important for the maternal success ŽSalmon, 1987; Levy ´ et al., 1995.. However, the results of the present study showed that capybara females did not kill their offspring due to lack of experience: both primiparous and multiparous females presented the same rate of offspring mortality. This study indicates that the birthplace was related to the infanticides. In maternity pens, there were significantly less infanticides than in reproduction pens. Perhaps the few infanticides in the isolation pens were related with the stress of the confined females, because of handling and transport for pen, due to the short time for adaptation to the new environment or the presence of strange animals in the neighboring pens that may have displayed aggressiveness. This fact corroborates the suggestion of Salmon Ž1987. in M. musculus, for which stress of the pregnant females can cause the infanticide of the newborn. In a peaceful place, the mother is more efficient in the care of the newborn, which elevates the reproductive success. Most of the infanticides were registered in reproduction pens containing animals that were not familiar. Either the females killed each other’s offspring or the mothers
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S.S.d.C. Nogueira et al.r Applied Animal BehaÕiour Science 62 (1999) 351–357
themselves could have killed their young in the moment of the cleaning, due to stress. If they feel in danger, there may be a risk of biting the offspring at this moment, causing deaths. We verified that in spite of the apparent harmonic conviviality among the females of the groups formed with adult animals, intolerance exists to the newborn. These facts suggest that the familiarity among the females should be taken into account for formation of reproduction groups, in order to eliminate the isolation for parturition. The present study suggests that in intensive breeding, the capybara females do not need isolation pens to give birth, as long as reproduction groups live together since weaning and no member removed and then reintroduced. In this way, expenses of building maternity pens and handling pregnant females can be cut down. This may also enable the reduction of interbirth intervals because they have ovulation during lactation ŽNogueira-Filho et al., submitted.. Also, both stresses during birth and possible rejection by groups after isolation can be reduced. Nevertheless, when there are animals of different origins living together in the same pen, the isolation is essential to avoid the occurrence of infanticides. This same rule is valid when reproduction of capybaras in semi-intensive system on larger areas is intended. In two commercial farms that we visited, infanticides were recorded after the introduction of unfamiliar individuals to the resident groups ŽFossalussa and Nespolo, personal communication..
Acknowledgements We are grateful to Dr. J. Ojasti for making many helpful suggestions and critically reviewing the manuscript. For Denise Rossi and Sabine Pompeia we thank the manuscript translate reviewed. The work was supported by a postgraduate grant to SSCN from CNPq ŽBrazil..
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