Kia Ora MARMAMers,
My co-authors and I are pleased to announce our recent publication of an international collaboration involving Massey University, Atlantic Technological University, Department of Conservation (DOC)
and our iwi partners to offer first insights to the reproduction of female common dolphins in New Zealand waters.
Abstract:
Reproductive biology was assessed in 106 female common dolphins (Delphinus
delphis) examined post-mortem from stranding and bycatch events along the New Zealand coastline between 1997 and 2019. The average age (ASM) and
length (LSM) at sexual maturity was estimated at 7.5 years and 183.5 cm, respectively. The total number of corpora in
mature individuals increased with age and appeared to persist throughout life. Ovarian asymmetry was apparent, with the left ovary displaying higher rates of ovulation, and a maximum of 19 corpora recorded
for a 24-year-old female. The estimated ovulation and annual pregnancy rates for mature females were 0.39 year−1 and
30%, respectively. Conception and calving occurred year-round, with a weak seasonal increase observed in late austral spring and early austral summer. As these data did not clearly show whether seasonality was present, the gestation, lactation, and resting
periods were calculated as either 12.6 or 12.8 months based on the presence/absence of seasonality, respectively. Similarly, calving interval ranged from 3.15 to 3.2 years, depending upon whether seasonality was considered. The estimated LSM of the New Zealand
population aligns with other populations globally, although the estimated ASM is younger by approximately 6 months. Other reproductive parameters align with Northern Hemisphere populations, although demonstrate variation, which may reflect adaptations to local
conditions such as water temperature and prey availability. As the species is subject to anthropogenic impacts including pollution and bycatch, we suggest our findings be used as a baseline with which to monitor trends in population parameters.
Open Access the full research from here: https://doi.org/10.1007/s00227-022-04139-3
Thank you very much and ngā mihi nui,
Emily