[MARMAM] New publication - Evidence for a postreproductive lifespan in female false killer whales

Theoni Photopoulou theoni.photopoulou at gmail.com
Fri Jun 23 02:57:04 PDT 2017

Dear all,

We are pleased to share our recent publication with you:

Theoni Photopoulou
Ines M. Ferreira,
​ ​
Peter B. Best,
​ ​
Toshio Kasuya and
Helene Marsh
​. ​2017.
Evidence for a postreproductive phase
​ ​
in female false killer whales Pseudorca crassidens
Frontiers in Zoology
​ ​

A substantial period of life after reproduction ends, known as
postreproductive lifespan (PRLS), is at odds with classical life history
theory and its causes and mechanisms have puzzled evolutionary biologists
for decades. Prolonged PRLS has been confirmed in only two non-human
mammals, both odontocete cetaceans in the family Delphinidae. We
investigate the evidence for PRLS in a third species, the false killer
whale, Pseudorca crassidens, using a quantitative measure of PRLS and
morphological evidence from reproductive tissues.
​ ​
We examined specimens from false killer whales from combined strandings
(South Africa, 1981) and harvest (Japan 1979-80) and found morphological
evidence of changes in the activity of the ovaries in relation to age.
Ovulation had ceased in 50% of whales over 45 years, and all whales over 55
years old had ovaries classified as postreproductive. We also calculated a
measure of PRLS, known as postreproductive representation (PrR) as an
indication of the effect of inter-population demographic variability. PrR
for the combined sample was 0.14, whereas the mean of the simulated
distribution for PrR under the null hypothesis of no PRLS was 0.02. The
99th percentile of the simulated distribution was 0.08 and no simulated
value exceeded 0.13. These results suggest that PrR was convincingly
different from the measures simulated under the null hypothesis.
​ ​
We found morphological and statistical evidence for PRLS in South African
and Japanese pods of false killer whales, suggesting that this species is
the third non-human mammal in which this phenomenon has been demonstrated
in wild populations. Nonetheless, our estimate for PrR in false killer
whales (0.14) is lower than the single values available for the
short-finned pilot whale (0.28) and the killer whale (0.22) and is more
similar to working Asian elephants (0.13).

​The article is open access

​All the best,

Theoni Photopoulou, Postdoctoral Fellow
Institute for Coastal and Marine Research, Nelson Mandela Metropolitan
University, South Africa
Centre for Statistics in Ecology Environment and Conservation, University
of Cape Town, South Africa
" Be silly. Be honest. Be kind " Ralph Waldo Emerson
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