Abstract Information about the social relations among individuals is essential to define and develop management plans for a socially structured population. Association data for 25 adult Lahille’s bottlenose dolphins were obtained from 189 photo-identification surveys that took place between January 2007 and May 2009 in La Coronilla-Cerro Verde and Cabo Polonio, Rocha, Uruguay. Group size averaged 5.22 individuals (SD= 3.77, n= 255). Coefficients of association were calculated using the Half-Weight Index. Most of the associations were weak (79.7%) and variation of real association indices was greater than would be expected by chance. Thus, the null hypothesis that individuals associated randomly was rejected. Standardized Lagged Association Rate analysis also indicated that nonrandom associations between individuals persisted over the study period. The exponential decay model that fits best to the data suggested the existence of constant companions and casual acquaintances. This study is the first report about the social structure of the population of Lahille’s bottlenose dolphin inhabiting the Uruguayan marine coasts. Cerro Verde and Cabo Polonio were the first marine protected areas selected by the government of Uruguay. However, information about the ecology and behavior of the species in these areas is still insufficient. It is recommended that the results of this study be taken as baseline information to assess the conservation status of this population, as well as for the development of adequate conservation and management plans.

Activity patterns are a fundamental aspect of the biology of many species, with important implications for survival and reproduction. Typically, such patterns of activity are thought to be entrained by light cues, raising intriguing questions about the nature of circadian rhythms in subterranean species, members of which spend virtually their entire lives in dark, underground burrows. As part of ongoing studies of the behavioural biology of the Rio Negro tuco-tuco (Ctenomys rionegrensis), we used data from free-living animals to characterize daily patterns of activity in this subterranean species of rodent. The locations of 5 radiocollared adults were recorded hourly for 72 consecutive hours during November, 2005. Analyses of 5 measures of activity based on these data revealed that individuals changed locations more often and moved greater distances between successive radio fixes during daylight hours. These data are consistent with studies of other ctenomyid rodents in suggesting that C. rionegrensis tends toward diurnality. Comparisons with other lineages of subterranean rodents indicate that activity patterns vary markedly among these burrow-dwelling mammals, with substantial intra- as well as inter-specific differences in activity reported.

Los patrones de actividad son un aspecto fundamental de la biología de muchas especies, con gran impacto en su sobrevivencia y reproducción. Típicamente, se considera que los patrones de actividad, aun siendo endógenos, se sincronizan con la luz, lo cual plantea interrogantes sobre la expresión de los ritmos circadianos en las especies subterráneas, cuyos miembros pasan virtualmente toda su vida en oscuras cuevas subterráneas. Como parte del estudio de la biología del comportamiento del tuco-tuco de Río Negro (Ctenomys rionegrensis), colectamos datos de animales en condiciones naturales para caracterizar el patrón diario de actividad en esta especie de roedor subterráneo. Se registró la localización de 5 individuos cada hora durante 72 horas consecutivas en noviembre 2005. El análisis de 5 medidas de actividad calculadas a partir de los datos mostró que los individuos cambian de localización más frecuentemente y se mueven mayores distancias durante el día. Esta tendencia a mayor actividad diurna es consistente con estudios realizados en otras especies de ctenómidos. Las comparaciones con otros roedores subterráneos muestran que el patrón de actividad diario es un rasgo muy variable, con importantes variaciones tanto dentro como entre especies.

Os peixes anuais habitam charcos temporários que secam sazonalmente, e as adaptações para sobreviver a estas condições extremas incluem altas taxas metabólicas e um elaborado comportamento de cortejo, que culmina com a deposição de ovos resistentes à dessecação dentro do substrato, os quais são capazes de atravessar estádios de diapausa. O pronunciado dimorfismo sexual apresentado por estes peixes indica que a seleção sexual poderia estar exercendo um papel chave na diferenciação, especiação e evolução deste grupo diverso de peixes. Entretanto, informações acerca dos mecanismos de isolamento reprodutivo, incluindo uma análise detalhada dos sinais de cortejo, são escassas. Neste artigo é analisado o comportamento reprodutivo de Austrolebias reicherti de maneira qualitativa e quantitativa. As unidades comportamentais utilizadas neste estudo correspondem àquelas incluídas em análises anteriores de outras espécies de peixes anuais. A unidade comportamental mais freqüentemente observada em machos foi a "exibição lateral", onde características espécie-específicas da morfologia e colorido são exibidas para a fêmea. A alta proporção de ocorrência (em freqüência e tempo) do comportamento de "quietude" nas fêmeas indica que o mesmo poderia desempenhar um papel avaliativo durante o cortejo. Outros sinais além dos visuais estão envolvidos no cortejo dos peixes anuais; os machos vibram as nadadeiras dorsal e anal e ondulam o corpo, o que indica que os sinais mecânicos poderiam ter influência na atração das fêmeas. Estes resultados conferem suporte à hipótese de sinais multimodais, recentemente proposta. Os movimentos de cortejo altamente conservados dentro de Austrolebias indicam que o reconhecimento específico e a barreira à hibridização poderiam não ocorrer nesta etapa, a menos que se encontrem diferenças quantitativas nestes sinais comportamentais.

Annual fishes inhabit temporary ponds that dry out seasonally and the adaptations to survive this extreme condition include high metabolic rates and an elaborate courtship behavior which ends in the deposition of drought-resistant eggs, capable of going through diapause stages in the substrate. The pronounced sexual dimorphism that these fishes show suggests that sexual selection could play a key role in the differentiation, speciation and evolution of this diverse group of fishes. However, there is scarce information about their reproductive isolation mechanisms, including detailed analysis of courtship signals. Herein, we analyzed, qualitatively and quantitatively, the reproductive behavior of Austrolebias reicherti. The behavioral units recognized in this study correspond with the previous analysis of other species of annual fishes. The most frequent unit in males was the lateral display where specific morphological and coloration patterns are displayed to the female. The female's high relative frequency and time of quietness suggest that this unit may have an evaluation role during courtship. In addition to visual displays during courtship, males perform vibrations of the dorsal and anal fins as well as body undulations; these indicate that mechanical signals may be important for attracting females. Our results support the hypothesis of multimodal signals. The conservation of behavioral patterns in courtship displays within Austrolebias suggests that species-level recognition and the barrier to hybridization may not occur at this stage, unless quantitative differences can be identified.