INVESTIGADORES
DEGRATI Mariana
artículos
Título:
Effects of Tour Boats on Dolphin Activity Examined with Sensitivity Analysis of Markov Chains
Autor/es:
SILVANA L. DANS; MARIANA DEGRATI; SUSANA N. PEDRAZA; ENRIQUE A. CRESPO
Revista:
CONSERVATION BIOLOGY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2012 vol. 26 p. 708 - 716
ISSN:
0888-8892
Resumen:
In Patagonia, Argentina, watching dolphins, especially dusky dolphins (Lagenorhynchus obscurus),
is a new tourist activity. Feeding time decreases and time to return to feeding after feeding is abandoned and
time it takes a group of dolphins to feed increase in the presence of boats. Such effects on feeding behavior
may exert energetic costs on dolphins and thus reduce an individual?s survival and reproductive capacity
or maybe associated with shifts in distribution. We sought to predict which behavioral changes modify the
activity pattern of dolphins the most. We modeled behavioral sequences of dusky dolphins with Markov chains.
We calculated transition probabilities from one activity to another and arranged them in a stochastic matrix
model. The proportion of time dolphins dedicated to a given activity (activity budget) and the time it took a
dolphin to resume that activity after it had been abandoned (recurrence time) were calculated. We used a
sensitivity analysis of Markov chains to calculate the sensitivity of the time budget and the activity-resumption
time to changes in behavioral transition probabilities. Feeding-time budget was most sensitive to changes in
the probability of dolphins switching from traveling to feeding behavior and of maintaining feeding behavior.
Thus, an increase in these probabilities would be associated with the largest reduction in the time dedicated
to feeding. A reduction in the probability of changing from traveling to feeding would also be associated with
the largest increases in the time it takes dolphins to resume feeding. To approach dolphins when they are
traveling would not affect behavior less because presence of the boat may keep dolphins from returning to
feeding. Our results may help operators of dolphin-watching vessels minimize negative effects on dolphins.(Lagenorhynchus obscurus),
is a new tourist activity. Feeding time decreases and time to return to feeding after feeding is abandoned and
time it takes a group of dolphins to feed increase in the presence of boats. Such effects on feeding behavior
may exert energetic costs on dolphins and thus reduce an individual?s survival and reproductive capacity
or maybe associated with shifts in distribution. We sought to predict which behavioral changes modify the
activity pattern of dolphins the most. We modeled behavioral sequences of dusky dolphins with Markov chains.
We calculated transition probabilities from one activity to another and arranged them in a stochastic matrix
model. The proportion of time dolphins dedicated to a given activity (activity budget) and the time it took a
dolphin to resume that activity after it had been abandoned (recurrence time) were calculated. We used a
sensitivity analysis of Markov chains to calculate the sensitivity of the time budget and the activity-resumption
time to changes in behavioral transition probabilities. Feeding-time budget was most sensitive to changes in
the probability of dolphins switching from traveling to feeding behavior and of maintaining feeding behavior.
Thus, an increase in these probabilities would be associated with the largest reduction in the time dedicated
to feeding. A reduction in the probability of changing from traveling to feeding would also be associated with
the largest increases in the time it takes dolphins to resume feeding. To approach dolphins when they are
traveling would not affect behavior less because presence of the boat may keep dolphins from returning to
feeding. Our results may help operators of dolphin-watching vessels minimize negative effects on dolphins.