The bottlenose dolphin, Tursiops truncatus, is a widely popular
marine mammal and the most common member of the family Delphinidae. The wild bottlenose
dolphin can be found worldwide in tropical and temperate waters. They are
commonly found in groups of 2 to 15 dolphins, although offshore herds are
sometimes comprised of several hundred individuals. Bottlenose dolphins use
echolocation to locate and capture prey, which consists of benthic
invertebrates and fish for coastal individuals, and pelagic squid and fish for
those offshore.
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| Figure 1. A small group of wild bottlenose dolphins |
The presence of wild
bottlenose dolphins in an area commonly generates strong public interest which
can result in an increase in boat activity. This can potentially cause altered
behavior and may pose a threat for the dolphins’ wellbeing. Several studies
have been done on small groups of coastal bottlenose dolphins and have observed
the dolphins spending more time underwater in order to avoid the boats.
However, a study was done in 2005 that aimed to study the diving behavior of a
solitary male bottlenose dolphin and determine if the presence of boats would
cause any behavioral changes.
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| Figure 2. A group of bottlenose dolphins seen near a boat |
The
study was done within a bay on the north-western coast of Spain. Daily
observations were made to study the male dolphin’s diving behavior, including
accurate measurements of the length of time spent in a dive. The results found
that the solitary male bottlenose dolphin did not change his diving behavior as
a result of boat presence. This may have been because the movement of the boats
in the bay were slow and predictable, or because the dolphin was habituated to
the stimulus of the boats. More studies are needed to figure out the exact effects
boats have on dolphin behavior and this type of study is important in helping
make more informed decisions on factors affecting the wellbeing of bottlenose
dolphins.
References:
Díaz
López, Bruno, et al. "Diving activity of a solitary wild free ranging
bottlenose dolphin (Tursiops truncatus
)." Journal of the Marine Biological Association of the United Kingdom,
vol. 88, no. 6, 2008, pp. 1153-1157. OhioLINK Electronic Journal Center,
doi:10.1017/S0025315408000921.
NOAA. “Bottlenose
Dolphin (Tursiops truncatus).” NOAA
Fisheries, 16 Jan. 2015,
www.nmfs.noaa.gov/pr/species/mammals/dolphins/bottlenose-dolphin.html.
I think it's interesting that, while groups have been observed to dive longer, the solitary individual did not seem to follow this behavior. I wonder if maybe this individual is an outlier? Alternatively, dolphins are very social animals, so maybe diving behavior is influenced by who's around - if one dolphin decides to dive longer, maybe others are more likely to follow. I also wonder why this dolphin was solitary - why wasn't he part of a pod like most dolphins?
ReplyDeleteThis was a really cool article. It was great reading considering we saw dolphins on our trip. I believe we only counted 5 dolphins in what I would assume was "the herd." It's hard to believe that some can get to be up to several hundred individuals! That's awesome. I would be interested to learn if dolphins are affected by people just on the shore like we were. It would be interesting to learn if the dolphins were just as interested in us as were in them!
ReplyDeleteHow boating activity causes changes in dolphin behavior is very interesting, especially since human activity increases with dolphin activity due to tourism. I wonder if dolphin behavior is changed potentiality not just by boats, but if people diving and snorkeling could change their behaviors too?
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