NORTH-WESTERN JOURNAL OF ZOOLOGY 10 (1): 93-100 ©NwjZ, Oradea, Romania, 2014 Article No.: 131802 http://biozoojournals.ro/nwjz/index.html

Site fidelity and habitat use of the Guiana , guianensis (: Delphinidae), in the estuary of the Paraguaçú River, northeastern

Renata Lúcia Guedes BATISTA1,2,*, Martin R. ALVAREZ1, Maria do Socorro Santos dos REIS1,3, Marta Jussara CREMER4 and Alexandre SCHIAVETTI1

1. Universidade Estadual de Santa Cruz – UESC, Rodovia Ilhéus - Itabuna, km16, Salobrinho – CEP 45.662-000 – Ilhéus, Bahia, Brazil. 2. Fundação Mamíferos Aquáticos, Hospital Veterinário da Faculdade Pio Décimo, Av. Tancredo Neves, Jabotiana, Aracaju, Sergipe, Brazil. 3. Instituto Mamíferos Aquáticos, Av: Pinto de Aguiar, Rua dos Radioamadores, 73, Pituaçu, Salvador, Bahia, CRP: 41.741-080, Brazil. 4. Laboratório de Nectologia, Departamento de Ciências Biológicas, Universidade da Região de Joinville, Cx. Postal 110, São Francisco do Sul, SC, CEP: 89240-000, Brazil. *Corresponding author, R.L.G. Batista, E-mail: [email protected]

Received: 12. July 2012 / Accepted: 29. July 2013 / Available online: 23. December 2013 / Printed: June 2014

Abstract. Site fidelity is the tendency of individuals to return to the same area repeatedly or to remain in a certain area for an extended period of time. Site fidelity has been documented in a number of species, including Sotalia guianensis. The aim of this study was to describe and estimate the range size of S. guianensis individuals and to determine its site fidelity. The study was conducted in the estuary of the Paraguaçu River and adjacent areas in the state of Bahia, northeastern Brazil. Field surveys were conducted during September and October 2005, August and October to December 2006, and July and August 2007, using a powerboat. Groups/individuals were approached cautiously to allow photographing the dorsal fin and position was recorded with GPS. Nicks and notches on the dorsal fin were used for individual identification. A total of 30 field surveys were conducted and 30 individuals were identified. A total of 135 groups were recorded, ranging in size from one to 55 individuals (median = 7, mean = 9.07 ± 6.12). The inclusion of new individuals ranged from zero (no record of new ) to six; twenty-eight individuals have been identified with 50% of the field surveys performed. The study revealed evidence of site fidelity and it may be observed that the individuals had been using the estuary for five or six years. The spatial distribution of the groups in the study area was not homogeneous. A total of 60.39% of the sightings occurred in areas with depths of 20 to 30 m (p<0.05), 45.88% occurred over gravel substrate and 44.41% occurred over silty clay substrate (p<0.01). The smallest individual range was 0.97 km2 and the largest stretched out on 8.76 km2; individuals’ ranges overlapped by approximately 0.50 km2 (mean = 4.88, SD – 2.44). However, animals with overlapping areas were seen together more than once in these sites. Considering the frequency of sightings for S. guianensis in the estuary of the Paraguaçu River, it seems that this population shows site fidelity. Moreover, the presence of some individuals in the area for at least six years indicates long-term site fidelity. The use of a small area and site fidelity draws one’s attention to the vulnerability of the Guiana dolphin and possible alterations that may occur in the habitat.

Key words: Sotalia guianensis, site fidelity, space use, Brazil.

Introduction some degree of regional site fidelity and limited movement patterns (Shane 1980). Site fidelity is Habitat is the type of place where an nor- the tendency of individuals to return to the same mally lives or, more specifically, the collection of area multiple times, or to remain in the area over a resources and conditions necessary for its occu- prolonged period, as occurs in the breeding and pancy (Garshelis 2000). Generally, habitats are feeding areas (White & Garrot 1990). Site fidelity composed of a mosaic of heterogeneous patches has been documented in a number of species that differ with regard to resources and both (Switzer 1993), including cetaceans, such as Tur- physical and biological conditions (Ballance 1992). siops truncatus (Defran & Weller 1999, Hubard et As a response to this heterogeneity, specific pat- al. 2004), hectori (Brager et al. terns of habitat used by are observed 2002) Sousa chinensis (Parra et al. 2006), Ziphius (Cremer 2000, Rossi-Santos et al. 2010). cavirostris and Mesoplodon densirostris (McSweeney Among cetaceans, protected habitats have et al. 2007). In Brazil, there are reports of some de- been found to foster relatively small school sizes, gree of site fidelity for the Guiana dolphin, Sotalia

94 R.L.G. Batista et al.

Figure 1. Location of Todos os Santos Bay in northeastern Brazil with emphasis on the estuary of the Paraguaçu River (study area).

guianensis (Flores 1999, Simão et al. 2000, Santos et The dynamics of the tide and river flow are regulated by al. 2001, Azevedo et al. 2004, Rossi-Santos et al. the Pedra do Cavalo reservoir. Salinity ranges from 30 to 2007, Wedekin et al. 2007, Hardt et al. 2010, 34, depending on the tide flow. The lowest temperatures (27 and 27.5°C) occur in June and August and the highest Oshima et al. 2010). temperatures (30.5 to 31.5°C) occur in September and Oc- The distribution of Sotalia guianensis is re- tober (Ramos 1993). stricted to the east coast of the Atlantic Ocean (da Field surveys were conducted for eight months dis- Silva & Best 1996, Flores & da Silva 2009). Studies tributed over three years (September and October 2005, have been carried out to describe the behavioral August and October to December 2006, and July and Au- patterns of the Guiana dolphin in the estuary of gust 2007) in the estuary of the Paraguaçu River and adja- the Paraguaçú River, located in Todos os Santos cent areas using a motorboat (model MNS 75). Each inde- pendent boat survey lasted from five to seven hours. Ac- Bay in the state of Bahia (BA), northeastern Brazil tive searches for individuals were performed with alter- (Spínola 2006, Reis et al. 2008). However, knowl- nate routes to the west (towards the river) and east (sea- edge on the ecological and social aspects of this wards). A sighting was defined as an encounter with ei- species in the area remains scarce. ther a group or solitary individuals during the course of a The aim of this study was to determine the site survey (Flores & Bazzalo 2004). A group was defined as a fidelity of S. guianensis in the estuary of River set of individuals, frequently - but not necessarily - en- Paraguaçu and estimate the size range of indi- gaged in the same behavioral activity or moving in the same direction (Shane 1990). viduals. Groups/individuals were approached cautiously to allow photographing the dorsal fin at a relatively close distance (< 50 m); the position was recorded with the aid Materials and methods of a handheld GPS. The start and end time of the sight- ings, number of individuals encountered and number of The study was conducted in the estuary of the Paraguaçu photos taken of each group were recorded. Nicks and River and adjacent areas (12°46'-12°52'S; 38°52'-38°42'W) notches of the dorsal fin were used for individual identi- in the state of Bahia, northeastern Brazil. This area estab- fication (Defran et al. 1990). lishes the connection between Iguape Bay and Todos os Evidence of site fidelity was evaluated by determin- Santos Bay (Genz et al. 2008), 40 km from the Atlantic ing the frequency of sightings, which was in turn calcu- Ocean (Fig. 1). The estuary of the Paraguaçu River, which lated by dividing the number of days an individual was is located on the west coast of Todos os Santos Bay, has seen by the total number of sampling days. Different an area of 127.9 km2; it is composed of three segments: the sightings of the same individual on the same day were lower course of the river, Iguape Bay and the Paraguaçú considered only once to avoid pseudoreplication. To ana- River channel (Genz et al. 2008). lyze the long term fidelity in the estuary of the Paraguaçu The estuary of the Paraguaçu River extends across 18 River, in addition to the recently collected data (2005 to km (Genz et al. 2008). The sedimentology of the region 2007) we also used information from the data bank (2000 consists of varying proportions of fine sand, silt and detri- to 2003). tal minerals; quartz and clay minerals are more evident. The geographic position of the groups/individuals Site fidelity and habitat use of the Guiana dolphin 95 was determined to characterize the habitat based on loca- 2007), these individuals had sighting frequencies tion, bathymetric data and sedimentary layers, withy data greater than 40% (Fig. 4). acquired from the Geosciences study database. The spatial distribution of the groups in the The geographic positions recorded on different sam- study area was not homogeneous (Figs 5-6). A to- pling days were used to estimate the range size for each S. guianensis individual in the estuary of the Paraguaçu tal of 60.39% of the sightings occurred in areas River. The mapping of the sighting points was performed with depths of 20 to 30 m (X2 = 214.04, p<0.05); using ArcGis 9.0®. The Animal Movement extension 45.88% occurred over a substrate of gravel and (Hooge & Eichenlaub 1997) was used to calculate the in- 44.41% occurred over a substrate of silty clay (X2 = dividual range by using the minimum convex polygon 125.18, p<0.01) (Fig. 7) method (Jenrich & Turner 1969, Mohr 1947, Stickel 1954). Fourteen individuals sighted at different loca- Being an objective method, it is not limited by distribu- tions were analyzed to determine the size of the tion assumptions. We did not test for autocorrelation be- 2 cause the use of this method minimizes the sensitivity of used area. The smallest area consisted of 0.97 km our analyses to dependence of successive data points and the largest area was 8.76 km2 (mean = 3.88, SD (Cooper & Randall 2007, Swihart & Slade 1985, 1997). = 3.44) (Table 1). The individual range of the 14 Moreover, we considered that there was sufficient time individuals overlapped by approximately 0.50 between readings to allow the movement of individual km2. However, animals with overlapping areas dolphins across their area, therefore suggesting that suc- were seen together more than once in these sites. cessive data points are not temporally dependent (Harris et al. 1990, Otis & White 1999, Rooney et al. 1998, Santos & Lacey 2011, Swihart & Slade 1997, White & Garrott Table 1. Size of individual range of Sotalia guianensis in 1990). the estuary of the Paraguaçu River, state of Bahia, northeastern Brazil, using the minimum convex poly- gon method.

Results Individual Geographic Individuals range size (Km²) points (n) A total of 30 field surveys were conducted. Nei- BFD#02 2.32 12 ther of the groups was observed on only one sur- BFC#03 3.19 17 vey. One hundred thirty-five groups were re- BFC#05 1.44 10 BFC#06 2.18 15 corded, ranging in size from one to 55 individuals BFA#09 5.18 21 (mean = 9.07, median = 7, SD = 6.12). BFC#10 2.91 14 A total of 3189 photos were taken, allowing BFB#11 1.51 17 the identification of 30 individuals. The inclusion BFC#12 4.63 10 of new individuals after each day of sampling BFC#13 5.76 12 ranged from zero (no record of new animals) to BFC#14 5.72 22 six. Sixteen individuals were identified (53.33%) BFC#15 8.76 19 on the sixth field survey. Twenty-eight individuals BAA#16 0.97 10 BFC#26 2.03 12 had been identified with 50% of the field surveys BFC#28 7.69 11 performed. In February 2006, the curve reached an Mean 3.88 - asymptote, with the identification of only one in- Standard deviation 2.44 - dividual (Fig. 2). BFC#19 was the individual with the lowest frequency (3.33% of sightings), whereas BCF#09 Discussion was recorded in 60% of the sightings. The mean frequency of sightings of individuals was 25.78% According to Bearzi et al. (2005), the ongoing dis- (SD = 15.01). Among the 30 individuals identified, covery of a few individuals throughout the year 29 (96.67%) were sighted more than once and nine after the curve has flattened is to be expected even individuals were sighted in more than 40% of the in the absence of immigration. The stabilization of surveys (Fig. 3). the cumulative curve in the estuary of the Para- The analysis of the photos taken in the estuary guaçu River suggests that a major portion of the of the Paraguaçu River before the study period re- individuals that could be identified in the popula- vealed that the individuals BFD#02 and BFC#10 tion was recorded. had been using the estuary for six years and The sighting frequency of the Guiana dolphin BFC#03 and BFC#14 had been using the estuary at the estuary of the Paraguaçu river was similar for five years. During the study period (2005 to to the ones of some other regions throughout its

96 R.L.G. Batista et al.

Figure 2. Saturation curve of Guiana dolphin (Sotalia guianensis) during field surveys in the estuary of the Paraguaçu River, state of Bahia, northeastern Brazil.

Figure 3. Sighting frequency of the Guiana dolphins identified (Sotalia guianensis) in the estuary of the Paraguaçu River, northeastern Brazil, between 2005 and 2007.

Figure 4. Registry of the years when the encountered individuals were sighted.

distribution, such as Guanabara Bay, southeastern (Meirelles 2005). In Caravelas, northeastern Brazil, Brazil, with 94.2% of new sightings (Azevedo et al. a small number of individuals were constantly re- 2004); North Bay, in the state of Santa Catarina, corded, and a large number of individuals were southern Brazil, with 86% (Flores 1999); and sighted more than once; moreover, some animals Iracema Beach, northeastern Brazil, with 43.75% were recorded in the estuary over three years

Site fidelity and habitat use of the Guiana dolphin 97

Figure 5. Bathymetry of the area used by Sotalia guianensis in the estuary of the Paraguaçu River, state of Bahia, northeastern Brazil.

Figure 6. Sedimentary facies of the area used by Sotalia guianensis in the estuary of the Paraguaçu River, state of Bahia, northeastern Brazil.

(Rossi-Santos et al. 2007). tus) that presents high new sightings rates (Hu- There are also indications of fidelity for other bard et al. 2004); however, for this species, there species of cetaceans, such as the Cuvier’s beaked are evidences of some transient individuals whales (Ziphius cavirostris), Blainville’s beaked (Defran & Weller 1999). There were no evidences whales (Mesoplodon densirostris) with a frequency of transient individuals at the Paraguaçu River es- of 40% and 33.9%, respectively (McSweeney et al. tuary. 2007), and the (Tursiops trunca- The dolphins’ long-term occupation of specific 98 R.L.G. Batista et al.

conditions found at Guanabara Bay in the state of , southeastern Brazil (Azevedo et al 2007). The greatest depth of the studied area was found at the Paraguaçu River channel (40 m). Ac- cording to Azevedo et al (2007), the preference for deeper waters may be related to the distribution and concentration of prey, as the channel’s region presents better water renovation rate and higher amount of dissolved oxygen (Kjerfve et al. 1997, Jablonski et al. 2006). Hence, the use of deeper waters with silty clay

Figure 7. Occurrence of groups of Sotalia guianensis in and gravel substrate contributes to the heteroge- relation to depth and sediment in the estuary of the neous distribution of the groups in the estuary of Paraguaçu River, northeastern Brazil. the Paraguaçu River. This is similar to the situa-

tion reported from the Babitonga Bay, state of areas might be related to the high concentration of Santa Catarina (southern Brazil), where there is a food resources, as it occurs in estuaries (Ballance concentration in the central region of the bay, 1992). However, information on the diet of the which consists of many islands, rocks and tidal Guiana dolphin and prey abundance in the Para- flats (Cremer 2007), and the findings from the guaçú River channel is scarce. According to M. S. Paraty Bay, state of Rio de Janeiro (southeastern Reis, Brazil (pers. commun. 2010), a large amount Brazil), where a greater concentration may be of the Atlantic anchoveta (Cetengraulis edentulus) is found in sites located on sandbars with mud (Lodi found in the area, which is considerably important 2002). Habitat heterogeneity and the biological re- to the local human community as fish bait. Among quirements of a species interact to produce distri- the 74 species of fish that occur in the Paraguaçú bution and habitat-use patterns and exert influ- River channel (M. S. Reis, Brazil pers. commun. ence on the size of the home range of an animal 2010), 6 species and 12 families are part of the diet (McNab 1963). of the Guiana dolphin, as shown by studies on the The area of the Paraguaçú River Channel used species throughout its distribution in Brazil (Lodi by the individuals was relatively small in com- 2002, Di Benedito & Ramos 2004, Cremer 2007, parison to the area estimated at the Babitonga Bay Daura-Jorge et al. 2011). According to the accounts (southern Brazil), which ranged from 1.66 km2 to of local fishermen, the Guiana dolphin uses the es- 25.7 km2 (Hardt et al 2010), and the North Bay in tuary to feed on shrimp (Penaeidae), Atlantic the state of Santa Catarina (southern Brazil), which anchoveta (Cetengraulis edentulus) and mullet ranged from 5.39 to 46.15 km2 (Flores & Bazzalo (Mugil sp.), which are also captured by the fisher- 2004, Wedekin et al. 2007). These small areas sug- men. Thus, the fidelity of the Guiana dolphin to gest that the area estimated in the estuary of the the Paraguaçú River channel may be related to the Paraguaçu River may represent a part of the home fact that this area has the necessary food resources range of the species within Todos os Santos Bay. to sustain the population, in addition to offering There are overlapping areas in the estuary of the shelter from predators. Paraguaçu River, in Caravelas, northeastern Bra- Such relationship between fidelity and food zil, North Bay (Flores & Bazzalo 2004) and also in resources is reinforced by their greater occurrence Babitonga Bay, south of Brazil (Hardt 2005). Thus, in areas with sedimentary facies of silty clay and the individuals likely select the same habitat in the gravel, which are the environment of choice of estuary of the Paraguaçu River or the overlap may demersal fish that make part of the Guiana dol- be related to the association between individuals phin’s diet. In southeastern Brazil, the demersal and their social organization (Batista 2008). fish are present in 75% of the diet of dolphins (Di The use of a small area may also be explained Benedito 2000). by the presence of sufficient resources. In areas The Guiana dolphin usually swims in shallow where prey density is high, dolphins are not waters (Lodi 2002, Simão & Polleto 2002, Santos forced to range over long distances in search for 2004, Cremer 2000, 2007), therefore in different food, resulting in a high degree of site fidelity conditions from those found in the Paraguaçu (Karczmarski 1999). According to Cremer (2007), River estuary, which is - in turn - similar to the the abundance of food resources is a key factor in Site fidelity and habitat use of the Guiana dolphin 99 the choice of preferential habitats of this small ce- Bearzi, G., Politi, P., Agazzi, S., Bruno, S. (2005): Occurrence and present status of coastal dolphins (Delphinus delphis and Tursiops tacean. The predisposition of some animals to re- truncatus) in the eastern Ionian Sea. Aquatic Conservation: main in a familiar site signifies that the site at issue Marine and Freshwater Ecosystems 15: 243–257. offers ideal conditions for the species, with bene- Brager, S., Dawson, S.M., Slooten, E., Smith, S., Stone, G.S., Yoshinaga, A. (2002): Site fidelity and along-shore range in fits that exceed the costs (Stamps 1995). Factors Hector’s dolphin, an endangered marine dolphin from New such as the size of the animal, habitat heterogene- Zealand. Biological Conservation 108: 281-287. ity and predation pressure may influence the size Connor, R.C., Wells, R.S., Mann, J., Read, A.J. (2000): The bottlenose dolphin social relationships in fission-fusion society. pp. 91-126. of the area used (Connor et al. 2000). In: Mann, J., Connor, R.C., Tyack, P.L., Whitehead, H. (eds), The use of a small area and site fidelity draws Cetacean societies: Field studies of dolphins and whales one’s attention to the vulnerability of the Guiana Chicago. The University of Chicago Press. Cooper, L.D., Randall, J.A. (2007): Seasonal changes in home ranges dolphin against possible alterations that may oc- of the giant kangaroo rat (Dipodomys ingens): a study of flexible cur in the habitat. Species with a high degree of social structure. Journal of Mammalogy 88: 1000–1008. site fidelity are vulnerable to population decline Cremer, M.J. (2000). Ecologia e conservação de Sotalia fluviatilis guianensis (Cetacea, Delphinidae) na Baía da Babitonga, litoral due to habitat degradation and loss, particularly norte de Santa Catarina. Dissertation. Universidade Federal de when such species occupy relatively restricted São Carlos, São Carlos, Brazil. habitats (Warkentin & Hernandez 1996). Despite Cremer, M.J. (2007): Ecologia e conservação de populações simpátricas de pequenos cetáceos em ambiente estuarino no sul being part of the Todos os Santos Bay Environ- do Brasil. Tese. 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