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We compared the diagnostic value of three noninvasive methods (radiography, ultrasound, and palpation) of evaluating reproductive status in females of a large viviparous skink, the blotched blue-tongued lizard (Tiliqua nigrolutea). Radiography could be used to identify postovulatory females during the periovulatory period. However, in early to mid-gestation, radiography did not allow differentiation of the relatively homogenous structures within the abdomen. In late gestation, once calcification of the embryonic skeleton had occurred, gestation could be diagnosed and embryos counted. Ultrasound allowed differentiation between preovulatory, postovulatory, and nonreproductive females during the periovulatory period. Ultrasound also allowed visualisation of follicles during the early and middle stages of gestation. However, the level of operator experience, and the misdiagnosis of artefacts limited the accuracy of diagnosis. In the later stages of gestation, ultrasound did allow the detection of identifiable features of the developing foetal unit (fluid-filled foetal membranes, independent movement of the embryo, and visualisation of the heartbeat). Colour Doppler imaging could be used to visualise embryonic blood flow. Ultrasonography was not useful in detecting the number of embryos present. Palpation during the periovulatory period could be used to detect follicles and determine whether ovulation had occurred. However, during the remainder of the gestation period, palpation was unable to differentiate reproductive condition. This study provides a basis for the diagnosis of reproductive condition and problems in viviparous reptiles. Each of the diagnostic techniques is useful at different stages of gestation, and the use of a combined approach will give the most information throughout the reproductive cycle. Zoo Biol 21:253-268, 2002. © 2002 Wiley-Liss, Inc.

We compared the diagnostic value of three noninvasive methods (radiography, ultrasound, and palpation) of evaluating reproductive status in females of a large viviparous skink, the blotched blue-tongued lizard (Tiliqua nigrolutea). Radiography could be used to identify postovulatory females during the periovulatory period. However, in early to mid-gestation, radiography did not allow differentiation of the relatively homogenous structures within the abdomen. In late gestation, once calcification of the embryonic skeleton had occurred, gestation could be diagnosed and embryos counted. Ultrasound allowed differentiation between preovulatory, postovulatory, and nonreproductive females during the periovulatory period. Ultrasound also allowed visualisation of follicles during the early and middle stages of gestation. However, the level of operator experience, and the misdiagnosis of artefacts limited the accuracy of diagnosis. In the later stages of gestation, ultrasound did allow the detection of identifiable features of the developing foetal unit (fluid-filled foetal membranes, independent movement of the embryo, and visualisation of the heartbeat). Colour Doppler imaging could be used to visualise embryonic blood flow. Ultrasonography was not useful in detecting the number of embryos present. Palpation during the periovulatory period could be used to detect follicles and determine whether ovulation had occurred. However, during the remainder of the gestation period, palpation was unable to differentiate reproductive condition. This study provides a basis for the diagnosis of reproductive condition and problems in viviparous reptiles. Each of the diagnostic techniques is useful at different stages of gestation, and the use of a combined approach will give the most information throughout the reproductive cycle. Zoo Biol 21:253-268, 2002. © 2002 Wiley-Liss, Inc.

We compared the diagnostic value of three noninvasive methods (radiography, ultrasound, and palpation) of evaluating reproductive status in females of a large viviparous skink, the blotched blue-tongued lizard (Tiliqua nigrolutea). Radiography could be used to identify postovulatory females during the periovulatory period. However, in early to mid-gestation, radiography did not allow differentiation of the relatively homogenous structures within the abdomen. In late gestation, once calcification of the embryonic skeleton had occurred, gestation could be diagnosed and embryos counted. Ultrasound allowed differentiation between preovulatory, postovulatory, and nonreproductive females during the periovulatory period. Ultrasound also allowed visualisation of follicles during the early and middle stages of gestation. However, the level of operator experience, and the misdiagnosis of artefacts limited the accuracy of diagnosis. In the later stages of gestation, ultrasound did allow the detection of identifiable features of the developing foetal unit (fluid-filled foetal membranes, independent movement of the embryo, and visualisation of the heartbeat). Colour Doppler imaging could be used to visualise embryonic blood flow. Ultrasonography was not useful in detecting the number of embryos present. Palpation during the periovulatory period could be used to detect follicles and determine whether ovulation had occurred. However, during the remainder of the gestation period, palpation was unable to differentiate reproductive condition. This study provides a basis for the diagnosis of reproductive condition and problems in viviparous reptiles. Each of the diagnostic techniques is useful at different stages of gestation, and the use of a combined approach will give the most information throughout the reproductive cycle. Zoo Biol 21:253-268, 2002. © 2002 Wiley-Liss, Inc.

We compared the diagnostic value of three noninvasive methods (radiography, ultrasound, and palpation) of evaluating reproductive status in females of a large viviparous skink, the blotched blue-tongued lizard (Tiliqua nigrolutea). Radiography could be used to identify postovulatory females during the periovulatory period. However, in early to mid-gestation, radiography did not allow differentiation of the relatively homogenous structures within the abdomen. In late gestation, once calcification of the embryonic skeleton had occurred, gestation could be diagnosed and embryos counted. Ultrasound allowed differentiation between preovulatory, postovulatory, and nonreproductive females during the periovulatory period. Ultrasound also allowed visualisation of follicles during the early and middle stages of gestation. However, the level of operator experience, and the misdiagnosis of artefacts limited the accuracy of diagnosis. In the later stages of gestation, ultrasound did allow the detection of identifiable features of the developing foetal unit (fluid-filled foetal membranes, independent movement of the embryo, and visualisation of the heartbeat). Colour Doppler imaging could be used to visualise embryonic blood flow. Ultrasonography was not useful in detecting the number of embryos present. Palpation during the periovulatory period could be used to detect follicles and determine whether ovulation had occurred. However, during the remainder of the gestation period, palpation was unable to differentiate reproductive condition. This study provides a basis for the diagnosis of reproductive condition and problems in viviparous reptiles. Each of the diagnostic techniques is useful at different stages of gestation, and the use of a combined approach will give the most information throughout the reproductive cycle. Zoo Biol 21:253-268, 2002. © 2002 Wiley-Liss, Inc.

In fusionefission social systems, associations are generally weak, but animals can associate preferentially, although the ultimate and proximate causes for such associations can be multiple and depend on the species. We applied a social network approach to a population of marked female mountain goats, Oreamnos americanus, characterized by a fusionefission social system in which associations between individuals are assumed to be weak. We analysed the composition of nursery groups of mountain goats from the Caw Ridge (Alberta, Canada) population from 2005 to 2008 to test whether kinship, repro- ductive status and differences in body mass affect associations. We hypothesized that close kin should associate more than unrelated individuals, and we expected females of similar reproductive status, age or body mass to associate more than dissimilar individuals. We used the half-weight index correcting for differences in gregariousness (HWIG) to calculate associations between dyads of females. Females did not associate at random. Immature females associated strongly with their mothers, whereas adult fe- males associated mainly with females of similar reproductive status. Reproductive females may associate because they share similar needs during lactation. Nonreproductive adult females and females with different reproductive status associated according to their relatedness. Body mass did not influence associations between females. To our knowledge, this is the first time that a multivariate approach has been used to describe association preferences. Our results reveal how this approach can be relevant when studying the social structure of a population because it highlights the interactions between factors influencing associations.