TY - JOUR
T1 - Sexual maturation in male long-finned pilot whales (Globicephala melas edwardii)
T2 - Defining indicators of sexual maturity
AU - Betty, Emma L.
AU - Stockin, Karen A.
AU - Smith, Adam N.H.
AU - Bollard, Barbara
AU - Orams, Mark B.
AU - Murphy, Sinéad
N1 - Publisher Copyright:
© 2019 American Society of Mammalogists, www.mammalogy.org.
PY - 2019/7/27
Y1 - 2019/7/27
N2 - Male reproductive biology is described for the Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii), a subspecies that regularly mass strands along the New Zealand coastline. Ten mass stranding events sampled over a 7-year period enabled assessments of key life history parameters. Sexual maturation in immature, maturing, and mature males was assessed using morphological data and histological examination of testicular tissue. Variation was observed in the age (11-15 years) and length (450-490 cm) at which individuals attained sexual maturity. Using Bayesian cumulative logit regression models, we estimated the average age and length at the attainment of sexual maturity to be 13.5 years and 472 cm, respectively. Combined testes weight, combined testes length, an index of testicular development (combined testes weight/combined testes length), and mean seminiferous tubule diameter were all good indicators of sexual maturity status. Combined testes length was the best nonhistological indicator, and all testicular measures were found to be better indicators of sexual maturation for G. m. edwardii than age or total body length. Sexual maturity was attained before physical maturity (> 40 years and 570 cm), and at a younger age and smaller body length than previously reported for Globicephala melas melas in the North Atlantic. Given the ease of collection, minimal processing, and applicability to suboptimal material collected from stranding events, future studies should assess the value of testicular size as an indicator of sexual maturity in pilot whales and other cetacean species. Estimates of the average age and length at sexual maturity for G. m. edwardii provided in this study may be used to inform population models required for conservation management of the subspecies, which is subject to high levels of stranding-related mortality.
AB - Male reproductive biology is described for the Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii), a subspecies that regularly mass strands along the New Zealand coastline. Ten mass stranding events sampled over a 7-year period enabled assessments of key life history parameters. Sexual maturation in immature, maturing, and mature males was assessed using morphological data and histological examination of testicular tissue. Variation was observed in the age (11-15 years) and length (450-490 cm) at which individuals attained sexual maturity. Using Bayesian cumulative logit regression models, we estimated the average age and length at the attainment of sexual maturity to be 13.5 years and 472 cm, respectively. Combined testes weight, combined testes length, an index of testicular development (combined testes weight/combined testes length), and mean seminiferous tubule diameter were all good indicators of sexual maturity status. Combined testes length was the best nonhistological indicator, and all testicular measures were found to be better indicators of sexual maturation for G. m. edwardii than age or total body length. Sexual maturity was attained before physical maturity (> 40 years and 570 cm), and at a younger age and smaller body length than previously reported for Globicephala melas melas in the North Atlantic. Given the ease of collection, minimal processing, and applicability to suboptimal material collected from stranding events, future studies should assess the value of testicular size as an indicator of sexual maturity in pilot whales and other cetacean species. Estimates of the average age and length at sexual maturity for G. m. edwardii provided in this study may be used to inform population models required for conservation management of the subspecies, which is subject to high levels of stranding-related mortality.
KW - New Zealand
KW - age
KW - body length
KW - cetacean
KW - male reproduction
KW - pilot whale
KW - sexual maturity
KW - testes
UR - http://www.scopus.com/inward/record.url?scp=85070110862&partnerID=8YFLogxK
U2 - 10.1093/jmammal/gyz086
DO - 10.1093/jmammal/gyz086
M3 - Article
AN - SCOPUS:85070110862
SN - 0022-2372
VL - 100
SP - 1387
EP - 1402
JO - Journal of Mammalogy
JF - Journal of Mammalogy
IS - 4
M1 - gyz086
ER -