Dear colleagues,
On behalf of my co-authors, I am pleased to announce the publication of the
following papers on subantarctic fur seal fasting capabilities and their ecological
implications. If you are interested in PDF copies, please email me at: ddlafouine@free.fr
Best wishes,
Delphine
PAPER #1:
Verrier, D.,
Groscolas, R., Guinet, C. and Arnould, J. P. Y. , Development of fasting
abilities in subantarctic fur seal pups: balancing the demands of growth under
extreme nutritional restrictions. Functional Ecology, no.
doi: 10.1111/j.1365-2435.2010.01823.x
Summary:
1. Surviving
prolonged food deprivation requires various metabolic adaptations such as
energy and protein sparing, which can be highly conflicting with
energy-demanding stages of an animal’s life history such as growth.
2.Due to
the maternal attendance pattern, subantarctic fur seal (Arctocephalus tropicalis
Gray) pups must repeatedly endure exceptionally long fasts of increasing
duration throughout the 10-month lactation period. Little is known of (i) how
these infants adapt to such extreme energetic constraints while sustaining
growth and development; and (ii) the ecological implications of repeated
prolonged fasting in early life in terms of offspring survival, maternal care
and growth strategy in this species, as well as the evolutionary consequences
of such life history trait.
3. Physiological
responses to
prolonged fasting and how they change with development throughout the
pre-weaning period were investigated. Results show that beginning with their
first fast, subantarctic fur seal pups are able to mobilize lipid reserves
preferentially while conserving protein stores in response to nutritional
deprivation. As pup age, profound changes in energy expenditure allow the
implementation of an efficient strategy of fat storage and lean body mass
preservation, which proves highly adaptive in the face of the low maternal
provisioning rates experienced.
4. Despite
increasing fasting durations, pup mortality decreased markedly throughout the
maternal dependence period. Consistent with predictions, field measurements
indicate that fasting endurance, although limited in early life, increases up
to durations of nearly 3 months with age. Results suggest that the
maternal provisioning strategy could be constrained by these ontogenetic
changes in pup fasting abilities.
5. Furthermore,
extreme energetic constraints and local density-dependent effects appear to
exert a strong selective pressure upon the adoption of a convergent growth
strategy between the sexes aiming to maximize fat storage and pre-weaning
survival.
6. The
issues of resulting trade-offs between pre- and post-weaning survival and the
evolutionary consequences of extreme fasting abilities are also addressed.
PAPER #2:
Verrier, D.,
Guinet, C., Authier, M., Tremblay, Y., Schaffer, S., Costa, D. P., Groscolas,
R. and Arnould, J. P. , The ontogeny of diving abilities in subantarctic fur
seal pups: developmental trade-off in response to extreme fasting?. Functional
Ecology, no.doi: 10.1111/j.1365-2435.2011.01846.x
Summary:
1. A
major hypothesis of life-history theory is that conditions of early development
affect future survival and reproductive success. Responses to detrimental
environments during early ontogeny may involve trade-offs between current and
future fitness. Yet, the functional mechanisms involved in such evolutionary
trade-offs remain poorly documented.
2. The physiological and behavioural ontogeny
of diving abilities was examined in subantarctic fur seal (Arctocephalus
tropicalis Gray) pups to assess whether the repeated extreme fasts they
naturally endure throughout the period of maternal dependence impacts on their
development.
3. The ontogeny of pup body oxygen storage
capacity was slow, in particular for the muscle compartment, which shows
limited increase in myoglobin content (0·23–0·85 g 100 g wet
muscle−1). As a consequence, by the time of weaning, mass-specific
oxygen stores had only reached 76%, 24% and 61% of adult female capacity for
blood, muscle and total, respectively. Concomitantly, in marked contrast to
other pinniped infants, they spent decreasing amounts of time in water (16–7%)
with age and exhibited very little diving experience and skills.
4. Overall, in addition to experiencing the
longest fasting durations throughout the maternal dependence period,
subantarctic fur seal pups demonstrate the lowest levels of mass-specific total
oxygen stores and maximum dive duration of any otariid near the age of weaning
reported to date.
5. Furthermore, dives that exceeded the
calculated aerobic dive limit occurred with a very low frequency (0·04%),
suggesting that behavioural limitations linked to the necessity to conserve
energy to survive repeated fasting, rather than restricted oxygen storage
capacity, constrained pup diving behaviour.
6. Hence, these animals appear to trade-off
the early development of both their physiological and behavioural diving
abilities in favour of body fat accumulation to survive the prolonged fasts
they must endure and, potentially, provide a nutritional buffer while they
locate appropriate food patches after weaning. While promoting pre-weaning
survival, this strategy renders pups more vulnerable to unpredictable changes
in environmental conditions and food availability at the transition to
independent foraging and, thus, could have negative impact on post-weaning
survival.
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Dr Delphine Verrier
DVM, PhD
Head of Primate Centre
Projet leader for the "Primatology and
Health" programme (URES)
International Centre for Medical Research
of Franceville (CIRMF)
B.P. 769, Franceville, Gabon
Phone : +241 67 70 62 / Mobile: +241 07 98 56 69
Email: ddlafouine@free.fr
Skype: ddlafouine1
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