Social proximities of developing gorilla males (Gorilla gorilla gorilla) in European zoos: The consequences of castration and social composition.

Applied Animal Behaviour Science 234 (January 2021) 105175. https://doi.org/10.1016/j.applanim.2020.105175

Abstract:

In the European captive population of western lowland gorillas (Gorilla gorilla gorilla), the harem social structure and an even sex ratio at birth result in a surplus of males and consequent management difficulties. This study seeks to assess the socialization differences between captive juvenile and adolescent male gorillas according to their fertility status (intact vs castrated) in different social compositions (familial vs bachelor groups), and to evaluate the suitability of castration as a management tool for the EEP gorilla population. We carried out social network analyses (SNA) to assess the “positive” proximity pattern of behaviour in 93 western lowland gorillas aged from 0 to 45 years old and housed in 11 social units (seven familial and four bachelor groups). We compared the data recorded for the 27 juvenile and adolescent (i.e. subadult and blackback) males included in our sample size. Although no differences were revealed between the intact juveniles and the castrated juveniles living in familial groups, our results showed that castrated adolescent individuals showed more cohesiveness within their familial group than their intact conspecifics in terms of their activity budget. They also displayed a “positive” proximity pattern of behaviour with all group members, including adults (silverback and females). Despite being significantly more isolated, the intact adolescent males living in bachelor groups do not differ from their castrated and intact counterparts of the same age class living in familial groups in terms of their strength of “positive” behaviour when close to group conspecifics. This effect highlights the social benefits of male-male interactions within gorilla species. Our results may be evidence that both of the management strategies compared here, i.e. bachelor groups and castration, could be appropriate socio-behavioural enrichments during juvenility and adolescence. These findings also highlight the need to continue investigations until the study subjects reach adulthood to validate and/or improve these tools for the welfare-compliant management of gorilla male surplus in captivity.

letang-biblio

Minimal-invasive Kastration von männlichen europäischen Landschildkröten.

Testudo (SIGS), 28(2): 20-25.

Volltext: https://www.sigs.ch/clubdesk/fileservlet?id=1000174

Einleitung:

Die Tatsache, dass es einen deutlichen Überschuss an männlichen europäischen Landschildkröten in der Schweiz gibt, sowie die oft beschränkte Gehegegrösse und der ausgeprägte Geschlechtstrieb der männlichen Schildkröten führen zu diversen Problemen. Die unkastrierten männlichen Landschildkröten verursachen eine ständige Unruhe im Gehege. Die Weibchen werden dauerhaft bedrängt und immer wieder entstehen mechanische Schäden am Carapax oder Deckverletzungen im Bereich der Kloake. Weiter führt das Aggressivitätsverhalten zwischen Männchen ebenfalls zu Bissverletzungen sowie eine deutliche Unruhe innerhalb der Gruppe. Diverse Methoden der chemischen Kastration wurden in den letzten Jahren erprobt. Leider haben weder das Verabreichen von weiblichen Hormonen noch dasjenige von Hormonen der Hirnanhangsdrüse zu einem erwünschten, voraussagbaren Erfolg geführt. In den letzten Jahren wurde die Technik der minimal-invasiven Endoskop-assistierten Kastration entwickelt.

sandmeier-biblio