Odorific communication by spraint deposition among
otters
(Lontra longicaudis)
This is an
experimental fieldwork to verify the role of the spraints in the intra-specific
communication among otters (Lontra longicaudis). It was carried out in
the Atlantic rain forest, at “Ribeirão de Iporanga” river (Iporanga, SP, Brazil). Otters
deposit spraints at conspicuous places, probably to flag their presence.
Researchers suspect that this behavior would be important in the communication
among the individuals sharing space and resources, and also for the
reproduction. Spraints depositions were mapped along 1.5 km in the river course,
during 12 months, totalizing 50 days of observations. We recorded 34 spraints
points that were used repeatedely along the year. The number of spraints found
during the winter was 6.4 times higher than it was in the summer. During the
dry winter, rain is scarce and spraints not washed away as in the summer, which
is rainy. Stones that emerge from the bank or the middle of the river were the
preferred sites for deposition (77% of the points). After having mapped the
area, an experiment to test if the otter tends to replace spraints if they were
removed. Spraints were removed from half of the points, along the river. After
3 days the points with new spraints deposition were counted. This experiment
was repeated 8 times, with an interval of one month between them. There wasn’t
a significant tendency of spraints deposition in the points where the scats
were removed (c2 = 4.748 p = 0.0931 g.l. = 2). A second
experiment was done to test if the otter react to the adding of spraints of
other individuals. Spraints from a
different river (16 km
apart) were laid in alternated points (50% for the experiment and 50% for
control). After 96 hours it was verified if new spraints were deposited on the
manipulated or controlled points. This experiment was repeated twice, with a
month interval. New spraints were deposited at a significantly higher frequency
in points where another otter’s spraints were laid (c2 = 8.531 p = 0.0035 g.l. = 1). We
conclude that spraints depositions by L. longicaudis reflect
optimization strategies to find more appropriate sites and for spraints
replacements.
