Presence Of Calves Research Articles

Cetacean diversity at the west coast of La Palma Island (Canary Islands)

Little is known about cetacean communities around La Palma Island. Therefore, and in order to determine the presence and distribution of the cetacean species on its west coast, daily censuses were carried out from November 2003 to April 2005. The platform used was a whale watching vessel certified by the Canary Government. Data collected included time, position, species identity, group size and, in some cases, the presence of calves and/or any other outstanding parameter. During the study period, 570 sightings were made, with a mean sighting success of 1.7 sightings per day, showing a high cetacean presence in the area. Thirteen species and one genus (Globicephalaspp.) were positively matched, three of them included in the Mysticeti suborder and the other ten in the Odontoceti one. The four most sighted species, in decreasing order, correspond toTursiops truncatus,Steno bredanensis,Globicephalaspp. andStenella frontalis. Diversity of sighted species shows a moderate peak during spring time, which is in agreement with the presence of occasional species. Most sightings were located off the central west coast of the island, exceeding 1.5 nautical miles. This is particularly outstanding in relation to Franja Marina de Fuencaliente SCI, where 90% of all sightings were located outside its boundaries. High cetacean presence and diversity off the west coast of La Palma Island seem to be connected with oceanographic and ecological features. Results gained provide, for this region, baseline data on cetacean populations and a useful tool in conservation plans.

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. 1,782 calves from 61 beef herds. Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.

Abundance and habitat preferences of the short-beaked common dolphin Delphinus delphis in the southwestern Mediterranean: implications for conservation

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 4:309-331 (2008) - DOI: https://doi.org/10.3354/esr00073 Abundance and habitat preferences of the short-beaked common dolphin Delphinus delphis in the southwestern Mediterranean: implications for conservation A. Cañadas1,*, P. S. Hammond2 1ALNITAK & SEC, Nalón 16, 28240 Hoyo de Manzanares, Madrid, Spain 2Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB, UK *Email: alnitak.ana@cetaceos.com ABSTRACT: The Mediterranean sub-population of short-beaked common dolphin is believed to have suffered a steep decline in the Mediterranean in recent years, and in 2003 it was listed as endangered in the IUCN Red List of Threatened Species. Effective conservation will depend critically on our understanding of the relationship between the species and its habitats. The Alborán Sea is believed to be the most important remaining Mediterranean habitat for this species, and thus constitutes a vital source of information for the development of conservation measures. We used spatial modelling to estimate the abundance and explore the habitat use of common dolphins in this area, examining regional, seasonal and interannual variations, as well as the influence of biological factors such as presence of calves, interspecific relationships and behaviour. From 1992 to 2004, 37385 km of non-systematic line transects generated 738 sightings in a 19189 km2 study area. The point estimate of abundance was 19428 (95% CI = 15277 to 22804) dolphins. Seasonal and geographical variations in abundance were detected, with higher average density in summer than in winter, and in the Western Alborán Sea than in the east Gulf of Vera, which has different physical/environmental characteristics. No overall trend in abundance was observed in the Alborán area. However, a decline was observed in the Gulf of Vera, with a summer density 3-fold lower in the period from 1996 to 2004 than in 1992 to 1995. A potential link of this decline with prey depletion due to the exponential growth of aquaculture in the area is discussed. Clear differences in habitat use were also found when examining the influence of biological factors. In particular, groups with calves and groups that were feeding preferred more coastal waters. This result could have important implications for the development of conservation measures for this species in the Mediterranean. KEY WORDS: Common dolphin · Mediterranean · Generalized Additive Models · GAMs · Abundance · Trends · Habitat use · Alborán Sea Full text in pdf format Supplementary appendix PreviousCite this article as: Cañadas A, Hammond PS (2008) Abundance and habitat preferences of the short-beaked common dolphin Delphinus delphis in the southwestern Mediterranean: implications for conservation. Endang Species Res 4:309-331. https://doi.org/10.3354/esr00073Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 4, No. 3. Online publication date: May 27, 2008 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2008 Inter-Research.

Vigilance Patterns of Territorial Guanacos (Lama guanicoe): The Role of Reproductive Interests and Predation Risk

AbstractWe conducted focal observations of territorial guanacos, a highly polygynous and social mammal, to compare time budgets between sexes and test the hypothesis that the differences in reproductive interests are associated with differential group size effects on male and female time allocation patterns. In addition, we used group instantaneous sampling to test the hypothesis that grouping improves detection capacity through increased collective vigilance. We fit GLM to assess how group size and group composition (i.e., presence or absence of calves) affected individual time allocation of males and females, and collective vigilance. As expected from differences in reproductive interests, males in family groups devoted more time to scan the surroundings and less to feeding activities compared to females. Both sexes benefited from grouping by reducing the time invested in vigilance and increased foraging effort, according to predation risk theory, but the factors affecting time allocation differed between males and females. Group size effects were significant when females were at less than five body‐lengths from their nearest neighbour, suggesting that grouping benefits arise when females are close to each other. Female time budgets were also affected by season, topography and vegetation structure. In contrast to our expectation, males reduced the time invested in vigilance as the number of females in the group increased, supporting the predation risk theory rather the intrasexual competition hypothesis. The presence of calves was associated with an increase in male individual vigilance; and vegetation type also affected the intensity of the group size effect over male time allocation. In closed habitats, collective vigilance increased with the number of adults but decreased with the number of calves present. Although male and female guanacos differed in their time allocation patterns, our results support the hypothesis that both sexes perceive significant antipredator benefits of group living.

The occurrence of bottlenose dolphins ( Tursiops truncatus) in the biological reserve of Atol das Rocas in north-eastern Brazil

The present work describes sightings of two groups of Tursiops truncatus , one with six and one with fifteen individuals, including four specimens identified by photograph and video, besides personal communications and records by other researchers. The presence of calves in the observed groups and the constant tactile interaction among the individuals suggest they may be using the area for socialization purposes. All the observations were taken on the north-western portion of the atoll which is the most sheltered throughout the year. The sightings of T. truncatus in the REBIO Atol das Rocas contribute to the knowledge about this species in Brazilian oceanic waters and highlight the importance of this area for the conservation of cetaceans.

Indications of fitness differences among vocal clans of sperm whales

Cultural variation can affect the genetic evolution of a species if there are consistent cultural differences that contribute to fitness variation between groups of individuals. In this study, measures of the reproductive success of groups of sperm whales from different cultural clans are used as proxies for fitness. We measure reproductive success using population length distributions from acoustic and photographic measurements and visual observations of the presence of calves. The results obtained are generally consistent between methods; there are large and significant differences between the clans in the measures of reproductive success. The results from this study strengthen the case for cultural hitchhiking in sperm whales by indicating that differences in culture between clans correlate with differences in fitness.

Influência da presença do bezerro no momento da ordenha sobre o desempenho reprodutivo de vacas mestiças Holandês-Zebu

Avaliou-se a influência da presença do bezerro no momento da ordenha sobre os parâmetros reprodutivos de 75 vacas primíparas e multíparas mestiças Holandês-Zebu, divididas em três grupos experimentais: GI - vacas ordenhadas sem a presença do bezerro; GII - vacas ordenhadas com a presença momentânea dos bezerros, sendo estes retirados da sala de ordenha logo após a descida do leite; e GIII - vacas ordenhadas com a presença constante dos bezerros, sendo estes amarrados ao lado da vaca durante toda a ordenha. O escore médio da condição corporal ao parto foi de 3,1. O período de serviço, dias para o retorno ao cio e as taxas de manifestação de cio e gestação até os 120 dias pós-parto não foram influenciados (P>0,05) pelo tipo de manejo de ordenha.

Are manatees modifying their vocalizations to compensate for noise?

Elevated environmental noise levels have the potential to interfere with the acoustic communication system of manatees by masking signals containing biologically important information. Communication theory recognizes several ways a sender can modify its acoustic signal to compensate for noise. These include increasing the source level of a signal, its repetition, its duration, or shifting frequency outside of the noise band. To test whether manatees can modify their vocalizations to compensate for noise, vocalization usage and structure were examined in terms of vocalization rate, duration, frequency, and source level. Results imply that manatees do increase their vocalization energy expenditure, or vocalization effort, as a function of behavior and calf presence. Increases in vocalization rate, duration, and source level were most pronounced when calves were present and during behaviors whereby animals tended to be more dispersed, which may suggest a cohesion function. In conditions of elevated noise levels, manatees increased call duration during feeding and milling behaviors when calves were present, suggesting that ambient noise levels do have a detectable effect on manatee communication and that manatees modify their vocalizations as a function of noise.

Seasonal and daily patterns of group size, cohesion and activity of the estuarine dolphin, Sotalia guianensis (P.J. van Bénéden) (Cetacea, Delphinidae), in southern Brazil

The resident population of estuarine dolphin, Sotalia guianensis (P.J. van Bénéden, 1864), in Norte Bay, Santa Catarina, southern Brazil, was studied from 2000 to 2003. Systematic one-day cruises were undertaken aboard a 5 m sail boat equipped with an outboard motor. Applying the focal-group method, information such as geographical position, predominant behavioural patterns, group size, cohesion index and the presence of calves, were registered at every five-minute interval, totalling 198 hours of direct observation of the dolphins. The estuarine dolphin used preferential areas for each behavioural pattern. The mean group size was approximately 29 individuals, and the presence of calves occurred throughout the entire year, but with a significant increase in the warm seasons. The frequency of behavioural patterns and group size varied according to season and time of day, and were strongly associated. The frequency of moving behaviours increased in the cold seasons and along the day. The seasonal variation in the moving behaviours suggest the requirement of a larger area in the cold seasons, probably related to seasonal fluctuations in the abundance of dominant prey items. Higher group sizes were observed while dolphins were foraging. The cohesion index also varied according to the behaviour. Our results showed that group organization and behavioural patterns of this estuarine dolphin population are probably linked to daily and seasonal environment cycles, and also possibly to the condition of being at the furthest southern limit of distribution of the species.

Padrões sazonais e diários do tamanho de grupo, coesão e atividade do boto-cinza, Sotalia guianensis (P.J. van Bénéden) (Cetacea, Delphinidae), no sul do Brasil

The resident population of estuarine dolphin, Sotalia guianensis (P.J. van Beneden, 1864), in Norte Bay, Santa Catarina, southern Brazil, was studied from 2000 to 2003. Systematic one-day cruises were undertaken aboard a 5 m sail boat equipped with an outboard motor. Applying the focal-group method, information such as geographical position, predominant behavioural patterns, group size, cohesion index and the presence of calves, were registered at every five-minute interval, totalling 198 hours of direct observation of the dolphins. The estuarine dolphin used preferential areas for each behavioural pattern. The mean group size was approximately 29 individuals, and the presence of calves occurred throughout the entire year, but with a significant increase in the warm seasons. The frequency of behavioural patterns and group size varied according to season and time of day, and were strongly associated. The frequency of moving behaviours increased in the cold seasons and along the day. The seasonal variation in the moving behaviours suggest the requirement of a larger area in the cold seasons, probably related to seasonal fluctuations in the abundance of dominant prey items. Higher group sizes were observed while dolphins were foraging. The cohesion index also varied according to the behaviour. Our results showed that group organization and behavioural patterns of this estuarine dolphin population are probably linked to daily and seasonal environment cycles, and also possibly to the condition of being at the furthest southern limit of distribution of the species.

Social influences on vigilance behaviour in giraffes, Giraffa camelopardalis

Vigilance in ungulates is considered to have a predominantly antipredator function, with the frequency and duration of scans per individual decreasing with increasing group size. Social influences on vigilance scans have been overlooked in studies on ungulates, although studies in primates and birds show that conspecific scans are important determinants of vigilance behaviour. We investigated group size effects in giraffes and examined social influences on their scanning behaviour, as well as the influence of feeding posture. We found that group size has little effect on scanning behaviour in either bulls or cows, which may be attributable to our inability to measure a group as perceived by a giraffe. Time spent scanning by lone cows did not differ from that of cows in any other group type, but time spent scanning by bulls when alone was less than that in groups. The presence of calves in a group did not influence scanning behaviour. Predation risk does not appear to be a significant modifier of vigilance behaviour, although a constant level of antipredator vigilance is probably maintained. Social factors were a significant modifier of vigilance scanning. Bulls scanned the most when they were in groups with larger bulls, and least when they were with smaller bulls. A similar pattern was seen with nearest-neighbour identity, and the identity of individuals within 10 m of a focal animal. Cows were significantly more vigilant when an adult bull was close, or was the nearest neighbour. Finally, vigilance advantages have been postulated as a determinant of sexual segregation in giraffe foraging heights but we found that the posture associated with high foraging heights imposes a vigilance cost, not an advantage. We therefore conclude that differential vigilance requirements are not a determinant of feeding height segregation between giraffe bulls and cows.

Group characteristics of marine tucuxis (Sotalia fluviatilis) (Cetacea: Delphinidae) in Guanabara Bay, south-eastern Brazil

Thirty-six boat surveys were conducted in Guanabara Bay, south-eastern Brazil, from October 2002 to June 2004 in order to investigate marine tucuxi group characteristics. The average and the range of tucuxis group size in the Guanabara Bay are similar with areas where small group sizes have been recorded. Group size ranged between one and 40 individuals (13·0±9·5; median=10·0). Groups of two to ten dolphins were the most common (53·9% of observations). Group size and the maximum number of dolphins sighted in each survey day did not vary between seasons (Kruskal–Wallis test, H3,36=3·249; P=0·355). Spatial geometry varied with group size and mixed groups were the largest (Kruskal–Wallis test, H3,218=57·149; P<0·001). The presence of calves had a great effect on group size, and nursery groups (mean =14·3±9·1; median=13·0) were twice as large than non-calf groups (mean=7·1±5·2; median=6·0). It is suggested that larger groups may aid in the calves development and learning. Group size changed frequently, resulting in 82·2% of observations with no constant size. Group size of marine tucuxi was not affected by the dolphins' behaviour (Kruskal–Wallis test, H2,215=5·626, P=0·06) neither by water depth (R2=0·012; F1,219=2·82; P=0·094).

Effects of Birth Date and Order in Lactation Performance of Iberian Red Deer (Cervus elaphus hispanicus)

This study discriminated between 2 effects (birth date and presence of older calves) assessed jointly in previous studies. Birth date delay produced similar effects to those reported previously: reduced milk and milk nutrient production in late-calving hinds, concentration of milk, substitution of protein by fat, greater body weight losses of dams (hinds), and reduced calf growth. Hinds in a group consisting of early- and late-born calves produced more milk, and calves grew more than their isolated counterparts. Evidence exists for consequences of foster suckling by early-born calves in mixed groups of early- and late-born calves at the end of the standard birth period, because these calves grew more than predicted by the milk production of their dams. In contrast, no detrimental effect was found in late-born calves of this group. Lack of differences might be due to the excess of hind milk production during the first 5 wk of lactation previously recorded in other experiments.

Bovine viral diarrhea (BVD)

Characteristics of bovine viral diarrhoea virus (BVDV), such as its genetic diversity and ability to induce a persistently infected (PI) carrier state, make its control a challenge. A systematic control programme that utilizes diagnostic testing strategies to identify PI cattle, vaccination to increase fetal protection from infection, and biosecurity to reduce the risk of exposure to infected animals is necessary for control of BVD. The primary reservoir for BVDV is PI cattle. If a herd has had recently confirmed PI calves, or if the history strongly suggests the presence of PI calves, then all calves, replacement heifers, bulls, and nonpregnant dams without calves should be tested for PI status. Positive cattle should be removed prior to the start of breeding. Because of the low prevalence of herds with PI animals, whole-herd screening protocols for herds at low risk for PI cattle may not be justified. Several strategies short of whole-herd screening can be employed to monitor herds for the presence of PI cattle. Biosecurity to reduce the risk of exposure to BVDV should also be implemented. Replacement heifers and bulls should be tested and confirmed PI-negative prior to the start of breeding. If a pregnant animal is purchased, she should be segregated until both dam and calf are confirmed PI-negative. Fence line contact with neighbouring herds should be avoided during early gestation unless they also have a strict biosecurity programme in place. Vaccination to reduce the risk of fetal infection in the event of exposure to a BVDV-shedding animal is an integral part of a biosecurity programme.

The Indo-Pacific Humpback Dolphin of the Arabian Region: A Status Review

Abstract Records of Indo-Pacific humpback dolphin sight-ings, strandings, and museum specimens in the Arabian region were compiled and used to review the distribution and status of this species. Nominal usage of Sousa chinensis (Osbeck, 1765) has been retained as a pragmatic measure, although the species present in the region resembles Sousa plumbea (Cuvier, 1828). Little is known about the ecology of this species in the region. Most available information on S. chinensis in the region originates from the Sultanate of Oman, where this species is among the most commonly recorded cetaceans; however, there is no absolute measure of abundance for anywhere in the region and the status of the species is unknown. Distribution is described for the region to include much of the Arabian (Persian) Gulf, Arabian Sea, Gulf of Aden, and Red Sea, but notably excludes the Gulf of Oman. This discontinuous distribution suggests the possible presence of discrete popu-lations within the region. Beach-cast/dead indi-viduals represent nearly two-thirds of all records (n=303) of this species in Oman. Live sightings indicate unusually large group sizes (up to 100 individuals) in the Arabian Sea and Arabian Gulf. Occasional associations with Tursiops sp. and Delphinus capensis tropicalis were documented. Mating behavior and the presence of calves were recorded in the months of April and May, and calves were also reported in June, October, November, and December. Threats to humpback dolphins in the Arabian region include incidental capture in fishing nets, coastal and offshore devel-opment (e.g., land reclamation, dredging, port and harbor construction), pollution, boat traffic, oil and gas exploration (including seismic survey-ing), military exercises, and biotoxins associated with red tide events. Evidence for historic and current directed catches of S. chinensis is limited, but opportunistic hunting may occur. Intraspecific variation in cranial measurements of individuals from the Arabian Sea coast of Oman fall within relative values found in individuals from the Saudi Arabian Gulf coast. Cranial abnormalities were few. Recommendations are made for conserva-tion management-oriented research focusing on stock identity and status assessments, as well as for monitoring of fisheries by-catch, clearer defi-nition of other threats, continued specimen and sample collection, and training of local scientists.Key Words: Humpback dolphin, Sousa, Arabia, Persian Gulf, Middle East, Oman, distribution, abundancy conservation

Residence Patterns, Group Characteristics, and Association Patterns of Bottlenose Dolphins Near Sanibel Island, Florida

A long-term, collaborative study of 385 individually recognizable bottlenose dolphins (Tursiops truncatus) near Sanibel Island in southwestern Florida revealed an open, fluid population including year-round and seasonal residents and transients. Less than 10% of the identified dolphins were seen for 10 yr or more, and new dolphins were identified throughout the study. Dolphin sightings peaked in the spring when prey species moved from the offshore Gulf of Mexico into the bays and nearshore Gulf. Group size averaged 5.5 dolphins (n = 561, SD = 4.22), and the factor which influenced group size most was the presence or absence of calves. Females were most likely and males least likely to be found in groups with calves. Associations between dolphins, measured by the simple ratio index, were generally low, indicating fluid relationships. The strongest and longest-lasting bonds were seen between pairs of males. A comparison of Sanibel dolphins with those in nearby Sarasota Bay showed that residence patterns were similar in the two areas and that apparent striking differences are lil{ely attributable to differences between research methods and an emphasis on long-term residents in Sarasota Bay as compared with an emphasis on variable residence patterns at Sanibel.

Association Between Persistently Bovine Viral Diarrhea Virus-Infected Calves and Pen Levels of Morbidity and Mortality in an Iowa Feedlot

As persistently infected (PI) cattle are the primary reservoirs of bovine viral diarrhea virus (BVDV) in cattle populations, there is general agreement that effective control of BVDV-induced losses requires the detection and elimination of these carriers from dairy and cowcalf herds. However, the significance of the presence of PI calves in pens of feedlot cattle is unknown. Our long-range goal is to determine whether identification and removal of PI calves prior to shipment to feedlots would be economically advantageous to feeders, and if such testing should be incorporated into preconditioning programs. As the first step toward answering this question, the objective of this study is to determine whether differences exist in morbidity and mortality in groups of calves that include PI calves and groups that do not include PI calves. If PI calves negatively impact morbidity and mortality, then future studies can be designed to examine the feasibility and economic impact of including BVDV PI testing in preconditioning programs.

Preliminary assessment of habitat characteristics of woodland caribou calving areas in the Claybelt region of Québec and Ontario, Canada

Woodland caribou (Rangifer tarandus caribou) require a diversity of forested habitats over large areas and may thus be particularly affected by the large-scale changes in the composition and age-class distribution of forest landscapes induced by the northern expansion of forest management. In this study we examine habitat characteristics associated to the use of calving areas by woodland caribou females and calves at different spatial scales. Thirty females were captured and collared with Argos satellite transmitters that allowed to locate 14 calving areas. Field surveys were conducted at each of these areas to measure the landscape composition of forest cover types and local vegetation characteristics that are used for both forage conditions and protection cover. At the scale of the calving area, univariate comparisons of the amount of forest cover types between sites with and without calves showed that the presence of calves was associated to mature black spruce forest with a high percent cover of terrestrial lichens. Within calving grounds, univariate comparisons showed that vegetation features like ericaceans and terrestrial lichens, that are important food resources for lactating females, were more abundant in calving areas where females were seen with a calf in mid-July than in areas where females were seen alone. The protection of the vegetation cover against predators was however similar between calving areas with or with¬out a calf. Logistic regression results also indicated that vegetation characteristics associated to forage conditions were positively associated to calf presence on calving grounds. Our results suggest that foraging conditions should be given more attention in analyses on habitat requirements of woodland caribou.

BOTTLENOSE DOLPHINS INCREASE BREATHING SYNCHRONY IN RESPONSE TO BOAT TRAFFIC

AbstractTo minimize potential impacts of boat traffic on the behavior of cetaceans it is important to assess short‐term behavioral responses to boats and interpret the long‐term consequences of these. Anecdotal descriptions of synchronous behavior in cetaceans are particularly frequent with reports of individuals within schools surfacing to breathe in a coordinated fashion being common. However, quantitative descriptions are rare. This study begins by quantifying synchronous breathing patterns of bottlenose dolphins off northern Scotland. We investigate possible functions of synchrony such as feeding patterns and presence of calves. We then test whether the presence of boat traffic in an area used intensively by dolphins affects their breathing synchrony. Although the majority of dolphin schools observed showed random breathing patterns, 30.5 % of schools showed synchronous breathing. There was no variation in this behavior with respect to identifiable feeding activities. However, synchrony was significantly negatively telated to the presence of calves in the school (χ2= 7.17, df = 1, P = 0.007) and significantly positively related to the presence of boat traffic in the study area (χ= 13.85, df = 1, P = 0.0002). Such consistent short‐term behavioral responses by dolphins may potentially accumulate to produce longer‐term consequences both for individuals and the whole population.

Sightings of Pontoporia blainvillei (Gervais & D' Orbigny, 1844) and Sotalia fluviatilis (Gervais, 1853) (Cetacea) in South-eastern Brazil

Pontoporia blainvillei (Gervais & D' Orbigny, 1844) and Sotalia fluviatilis (Gervais, 1853) have typically coastal habits and are sympatric in South-eastern Brazil. The purpose of this work was to record sightings and describe aspects concerning the behaviour of both species in this region, between 1993 and 1998. The sightings were accomplished by cruises and from a fixed point. Information provided by fishermen were also considered. In general, P. blainvillei was observed in all seasons of the year, up to five nautical miles away from the coast, up to 15 m deep and the groups comprised up to five specimens. The most part of the groups of S. fluviatilis, were observed in autumm and winter times and comprised up to 10 specimens. In about half of the sightings, the presence of calves and/or juveniles was noted. The cooperative (group) fishing was the foranging behaviour most frequently noted for S. fluviatilis.