The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds

Most non-avian theropod dinosaurs are characterized by fearsome serrated teeth and sharp recurved claws. Interpretation of theropod predatory ecology is typically based on functional morphological analysis of these and other physical features. The notorious hypertrophied ‘killing claw’ on pedal digit (D) II of the maniraptoran theropod Deinonychus (Paraves: Dromaeosauridae) is hypothesized to have been a predatory adaptation for slashing or climbing, leading to the suggestion that Deinonychus and other dromaeosaurids were cursorial predators specialized for actively attacking and killing prey several times larger than themselves. However, this hypothesis is problematic as extant animals that possess similarly hypertrophied claws do not use them to slash or climb up prey. Here we offer an alternative interpretation: that the hypertrophied D-II claw of dromaeosaurids was functionally analogous to the enlarged talon also found on D-II of extant Accipitridae (hawks and eagles; one family of the birds commonly known as “raptors”). Here, the talon is used to maintain grip on prey of subequal body size to the predator, while the victim is pinned down by the body weight of the raptor and dismembered by the beak. The foot of Deinonychus exhibits morphology consistent with a grasping function, supportive of the prey immobilisation behavior model. Opposite morphological trends within Deinonychosauria (Dromaeosauridae + Troodontidae) are indicative of ecological separation. Placed in context of avian evolution, the grasping foot of Deinonychus and other terrestrial predatory paravians is hypothesized to have been an exaptation for the grasping foot of arboreal perching birds. Here we also describe “stability flapping”, a novel behaviour executed for positioning and stability during the initial stages of prey immobilisation, which may have been pivotal to the evolution of the flapping stroke. These findings overhaul our perception of predatory dinosaurs and highlight the role of exaptation in the evolution of novel structures and behaviours

Song plasticity over time and vocal learning in clay-colored thrushes

Songbirds have been traditionally classified into close-ended or open-ended learning species according to the length of the sensitive period during which birds are able to memorize new vocalizations. Closed-ended learners are generally not capable of changing their song after the first year of life, while open-ended learners show song plasticity as adults. A few Turdus species have been sug- gested to be open-ended learners, but no long-term study has been conducted to investigate their song plasticity over time. We analyzed the songs of clay-colored thrushes, T. grayi, over four successive breeding seasons to assess song plasticity in their syllable repertoires within and between breeding seasons. A total of 16,262 syllables were classi- fied through visual inspection of spectrograms and multi- dimensional scaling analysis based on spectrogram correlations. On average, 563 ± 153 (SD) syllables per male per breeding season were analyzed. Male repertoire size was 9–20 syllable types. Males were capable of modifying their syllable repertoire between the initial and final periods of the breeding season. Song plasticity within breeding seasons may be associated with imitation between neighboring males, suggesting song learning in males that were C2 years old. This short-term plasticity is not enough, however, to explain the high proportion of change (mean = 65 % syllable types) in repertoire composition between breeding seasons in adult males. Song plasticity resulting from annual changes in repertoire composition could be explained by open-ended learning, but another mechanism, extended memory and re-expression, could also explain long-term plasticity. Experimental studies controlling the acoustic environment are needed to determine which mechanism is responsible for such a high level of song plasticity.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Vocal divergence and new species in the Philippine hawk owl Ninox philippensis complex

Volume: 28Start Page: 1End Page: 2

Mulheres cuidando de mulheres: um estudo sobre a Casa de Apoio Viva Maria, Porto Alegre, Rio Grande do Sul, Brasil Women caring for women: a study on the "Viva Maria" shelter, Porto Alegre, Rio Grande do Sul, Brazil

Este trabalho teve como objetivo obter dados a respeito de mulheres vitimizadas que são atendidas em uma casa abrigo governamental denominada "Casa de Apoio Viva Maria", situada na cidade de Porto Alegre. Analisaram-se informações referentes a 110 mulheres que estiveram albergadas na casa durante os últimos dois anos - janeiro de 1996 a junho de 1998. O perfil da clientela mostrou que as mulheres eram jovens - em média, 29 anos; todas de baixa renda; 12% analfabetas, 21% negras, 80% delas com história de violência doméstica freqüente. Além disso, 18% destas mulheres retornaram à relação com o companheiro violento. Foram efetuadas visitas domiciliares a 34 ex-moradoras, convidando-as a participar de uma série de oficinas de avaliação. Um total de 118 pessoas - mães e crianças - integrou os três encontros de avaliação. Durante estes, os pesquisadores estimularam as participantes a expressar suas opiniões, percepções e sentimentos a respeito da experiência vivida na casa abrigo, assim como seus conceitos no tocante à violência. Finalmente, realizou-se um grupo focal com a equipe técnico-administrativa da casa. As trabalhadoras enfatizaram o quanto esse tipo de trabalho tem sido útil para seu desenvolvimento pessoal e auxiliou a modificar suas vidas.<br>This research was conducted in Porto Alegre, Rio Grande do Sul, with a sample of battered women selected from a government shelter called the "Casa Viva Maria". We analyzed data on 110 women staying at the shelter during the previous two years (January 1996-June 1998). The profile of the women was as follows: abused women were young (mean age 29 years), all had low socioeconomic status, 12% were illiterate, 21% were black, 80% reported frequent abuse by their partners, and 18% had returned to violent homes. The researchers visited 34 former lodgers from the shelter and invited them to participate in a series of evaluation workshops. A total of 118 persons, including mothers and children, attended three evaluation meetings. During this process, researchers encouraged participants to express opinions, perceptions, and feelings about their past experience in the shelter and their own concept of violence. Finally, a focal group was organized with the "Viva Maria" staff members. Female workers reported how their job had been helpful for their personal development and had helped change their own lives