Page 183 - Demo

Proceptive vocalisations in orang-utan females1818who appeared to produce long calls spontaneously during ovulation when she was still reproductively active. In this anecdotal report, we (1) describe the behaviours of Temmy and Eloise, and (2) describe the structure of their vocalisations.MethodTemmyGroup and housingData for the first case were gathered in Allwetter Zoo (Münster, Germany). During the first study period (23-05-2022 until 27-05-2022), the zoo housed five adult Bornean orang-utans (4F, 1M; Supplementary Table 1). During the second study period (29-07-2022 until 30-07-2022) a new male was also present, who had recently been transported to the zoo. The orang-utan enclosure consisted of an indoor and outdoor enclosure, each capable of housing a subgroup. Alternatively, they could be connected to form one large enclosure. Temmy, the female of interest in this case, had been living in Allwetter Zoo for over 20 years at the time of research. She had not been exposed to a flanged male since the death of the previous flanged male at the start of 2020. During the first study period, Temmy was housed solitarily in the outside enclosure until ±15.30, when Mr. Miyagi was also allowed to move to the outside enclosure. During the second study period, Temmy and unflanged male Mr. Miyagi were housed together (either in the indoor or the outdoor enclosure), while the rest of the group was already introduced to the new flanged male Ramon.Female ovulationWhile we lack hormonal evidence of ovulation, multiple lines of evidence suggest that Temmy was ovulating during our first observation period. Firstly, because of a breeding recommendation by the EEP, Temmy was not on contraceptives. Secondly, according to the curator and the orang-utan caretakers, Temmy started the peri-ovulatory period of her menstrual cycle right before the first study period. Thirdly, the caretakers had observed a cooperative mating event between Mr. Miyagi and Temmy on the evening of 22-05-2022, two days prior to the start of our study. While sexual activity is not restricted to the peri-ovulatory period, it is much more likely to occur during this period (Durgavich et al., 2023). In orang-utans, Tom Roth.indd 181 08-01-2024 10:42