Biology Reference
In-Depth Information
Chapter 2
S
EASONAL
E
COLOGY OF
I
NIA IN
T
HREE
R
IVER
B
ASINS OF
S
OUTH
A
MERICA
(O
RINOCO
,
A
MAZON
,
AND
U
PPER
M
ADEIRA
)
Tamara L. McGuire
1
and Enzo Aliaga-Rossel
2
1
LGL Alaska Research Associates, Anchorage, AK, USA
2
Instituto de Ecología, Universidad Mayor de San Andres, La Paz, Bolivia and
University of Hawaii, Honolulu, Hawaii, USA
A
BSTRACT
Compared to most marine odontocetes, river dolphins live in an environment that is
less-stable and more spatially complex than the ocean. Yearly seasonal fluctuations in
river levels may be as great as 20 meters, and lead to seasonal extremes in quality and
quantity of aquatic habitat available to river dolphins. Seasonal changes in water levels
also affect the availability of dolphin prey due to seasonal patterns of fish reproduction
and fish migrations. Human-induced threats to river dolphins, such as incidental net
entanglement, vessel strikes, and deliberate killing appear to vary seasonally as well. In
this chapter, we present our investigations of the seasonal ecology of
Inia
spp from three
river basins of South America (
Inia geoffrensis humboldtiana
in Venezuela's Orinoco
River Basin,
Inia geoffrensis geoffrensis
in Peru's Amazon Basin, and
Inia boliviensis
in
Bolivia's Mamor￩ Basin). We provide results from our observational studies (which
included boat- based surveys of groups and photo-identification of individuals) and we
discuss these results in the context of other information about the seasonal ecology of
Inia
, including distribution, movement patterns, group size, age-class composition, and
seasonality of reproduction. We conclude with a discussion of how seasonal ecology
should be considered in the conservation of river dolphins and of the management of
human activities that affect them.
Keywords
: seasonal ecology, seasonality, distribution, movement patterns, group size, age-
class composition, reproduction, river dolphins, South American,
Inia boliviensis
,
Inia
geoffrensis
.
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