[MARMAM] Now available online: Whale and dolphin behavioural responses to dead conspecifics

Giovanni Bearzi giovanni.bearzi at gmail.com
Thu Jun 7 21:24:52 PDT 2018


Dear colleagues,

the final version of our article "Whale and dolphin behavioural responses
to dead conspecifics" is now available online, containing full
bibliographic details.

The Share Link below provides 50 days' free access to our article. Anyone
clicking on this link before July 27, 2018 will be taken directly to the
final version of the article (no sign up, registration or fees are required)

*Share Link: https://authors.elsevier.com/a/1XB203MhxMSrGv
<https://authors.elsevier.com/a/1XB203MhxMSrGv>*

If the link does not work, you may still contact the first author (
giovanni.bearzi at gmail.com) to receive a pdf file.


Highlights
• Effort-weighted study of 'postmortem attentive behaviour' (PAB) in
cetaceans.
• Dolphins (Delphinidae) accounted for 92.3% of 78 PAB records, baleen
whales 1.3%.
• Encephalisation was an important predictor of PAB across taxa.
• Female PAB towards dead calves (75%) may have been rescue attempts or
grieving.
• Male PAB was rare and possibly not caregiving.

Abstract
The scientific study of death across animal taxa—comparative
thanatology—investigates how animals respond behaviourally, physiologically
and psychologically to dead conspecifics, and the processes behind such
responses. Several species of cetaceans have been long known to care for,
attend to, be aroused by, or show interest in dead or dying individuals. We
investigated patterns and variation in cetacean responses to dead
conspecifics across cetacean taxa based on a comprehensive literature
review. We analysed 78 records reported between 1970 and 2016, involving 20
of the 88 extant cetacean species. We adopted a weighted comparative
approach to take observation effort into account and found that odontocetes
(toothed cetaceans) were much more likely than mysticetes (baleen whales)
to attend to dead conspecifics. Dolphins (Delphinidae) had the greatest
occurrence of attentive behaviour (92.3% of all records), with a weighed
attendance index 18 times greater than the average of all other cetacean
families. Two dolphin genera, Sousa and Tursiops, constituted 55.1% of all
cetacean records (N = 43) and showed the highest incidence of attentive
behaviour. Results of analyses intended to investigate the reasons behind
these differences suggested that encephalisation may be an important
predictor, consistent with the "social brain" hypothesis. Among attending
individuals or groups of known sex (N = 28), the majority (75.0%) were
adult females with dead calves or juveniles (possibly their own offspring,
with exceptions), consistent with the strong mother-calf bond, or, in a few
cases, with the bond between mothers and other females in the group. The
remaining records (25.0%) involved males either showing sexual interest in
a dead adult or subadult, or carrying a dead calf in the presence of
females. Because an inanimate individual is potentially rescuable,
responses to dead conspecifics—especially by females—can be explained at
least in part by attempts to revive and protect, having a clear adaptive
value. In some cases such responses are followed by apparently maladaptive
behaviour such as the long-term carrying of, or standing by, a decomposed
carcass, similar to observations of certain terrestrial mammals. Among the
possible explanations for the observed cetacean behavioural responses to
dead conspecifics are strong attachment resulting in a difficulty of
"letting go"—possibly related to grieving—or perhaps individuals failing to
recognise or accept that an offspring or companion has died. Our current
understanding is challenged by small sample size, incomplete descriptions,
and lack of information on the physiology and neural processes underpinning
the observed behaviour. We provide research recommendations that would
improve such understanding.


- - - - - - -
Giovanni Bearzi
President, Dolphin Biology and Conservation
<http://www.dolphinbiology.org/>
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