478
the niche partitioning system in Babitonga Bay. This fact, combined with small
franciscana population size, makes the latter highly vulnerable to local extinction.
Keywords Pontoporia blainvillei • Sotalia guianensis • Population • Southern
Brazil • Conservation
17.1 Introduction
Long-term monitoring of habitat use patterns is important for understanding population trends and identifying potential threats for the species (Krebs 2008).
Monitoring programs enhance our knowledge of species life history traits such as
population size (Wilson et al. 1999), migration patterns (Rock et al. 2006), distribution (Williams et al. 1993), critical habitats (Ingram and Rogan 2002), and social
structure (Whitehead 2008), and help us to identify changes in home range, residence patterns, and behavior, among others.
Recognition of individual animals in a population allows researchers to analyze
individual residence levels, providing critical information on temporal investment
in specific geographic areas (Wells and Scott 1990). This information can help us
estimate the relevance of specific areas for survival of the population.
Photoidentification is a non-invasive technique used for recognition of individual
animals (Würsig and Jefferson 1990). Natural body marks are reliable distinguishing features among cetaceans, and are thus commonly used in ecological studies
and to inform species conservation and management plans (Gomez-Salazar et al.
2011).
Sympatry describes the scenario in which two ecologically similar species share
the same habitat (Ricklefs 1996). Sympatric species may exploit the same resources,
potentially acting as competitors when resources are limited (Pianka 1983). Niche
separation and specialization help species to avoid direct interaction, and many
authors have suggested that ecologically similar species exhibit stronger differences
when they co-occur geographically than when they occur in non-overlapping parts
of a territory (Pulliam 2000; Bonesi et al. 2004). For cetaceans, ecological separation between sympatric species is based on differences in diet and habitat use
(Bearzi 2005). Species distribution is directly related to competition, dispersal,
niche size, resource availability, and habitat stability over time and space (Pulliam
2000). Depending on the spatial scale of analysis, populations tend to show patterns
of aggregation that depend on specific habitat characteristics. Resources are generally not randomly or regularly distributed, but rather concentrated in certain areas.
This aggregated resource distribution results in aggregated distribution of dolphin
populations (Begon et al. 1996).
Many small cetacean species occur in broad sympatry (sensu Bearzi 2005), in
which two or more species co-occur over a wide geographic area. One example is
Pontoporia blainvillei (Pontoporiidae), known as franciscana dolphin, and Sotalia
M.J. Cremer et al.
the niche partitioning system in Babitonga Bay. This fact, combined with small
franciscana population size, makes the latter highly vulnerable to local extinction.
Keywords Pontoporia blainvillei • Sotalia guianensis • Population • Southern
Brazil • Conservation
17.1 Introduction
Long-term monitoring of habitat use patterns is important for understanding population trends and identifying potential threats for the species (Krebs 2008).
Monitoring programs enhance our knowledge of species life history traits such as
population size (Wilson et al. 1999), migration patterns (Rock et al. 2006), distribution (Williams et al. 1993), critical habitats (Ingram and Rogan 2002), and social
structure (Whitehead 2008), and help us to identify changes in home range, residence patterns, and behavior, among others.
Recognition of individual animals in a population allows researchers to analyze
individual residence levels, providing critical information on temporal investment
in specific geographic areas (Wells and Scott 1990). This information can help us
estimate the relevance of specific areas for survival of the population.
Photoidentification is a non-invasive technique used for recognition of individual
animals (Würsig and Jefferson 1990). Natural body marks are reliable distinguishing features among cetaceans, and are thus commonly used in ecological studies
and to inform species conservation and management plans (Gomez-Salazar et al.
2011).
Sympatry describes the scenario in which two ecologically similar species share
the same habitat (Ricklefs 1996). Sympatric species may exploit the same resources,
potentially acting as competitors when resources are limited (Pianka 1983). Niche
separation and specialization help species to avoid direct interaction, and many
authors have suggested that ecologically similar species exhibit stronger differences
when they co-occur geographically than when they occur in non-overlapping parts
of a territory (Pulliam 2000; Bonesi et al. 2004). For cetaceans, ecological separation between sympatric species is based on differences in diet and habitat use
(Bearzi 2005). Species distribution is directly related to competition, dispersal,
niche size, resource availability, and habitat stability over time and space (Pulliam
2000). Depending on the spatial scale of analysis, populations tend to show patterns
of aggregation that depend on specific habitat characteristics. Resources are generally not randomly or regularly distributed, but rather concentrated in certain areas.
This aggregated resource distribution results in aggregated distribution of dolphin
populations (Begon et al. 1996).
Many small cetacean species occur in broad sympatry (sensu Bearzi 2005), in
which two or more species co-occur over a wide geographic area. One example is
Pontoporia blainvillei (Pontoporiidae), known as franciscana dolphin, and Sotalia
M.J. Cremer et al.