Heterarchy Reveals Social Organization of a Smooth Stingray (Bathytoshia brevicaudata) Population in a Provisioned Food Context

The advent of new technologies and statistical analyses has provided valuable insights into chondrichthyan social behavior. It has become apparent that sharks and rays lead more complex social lives than previously believed. Heterarchy combines hierarchy and social network theory and although it is not a new concept, it is rarely applied to animal social interactions. Here, we applied heterarchy to a case study involving smooth stingrays foraging for fish scraps at boat ramp in Jervis Bay, NSW Australia. We took advantage of their attraction to this site to examine their social behavior during agonistic interactions over the provisioned resource. We observed a stable, relatively linear but shallow dominance hierarchy that was highly transitive dominated by a single individual. Social network analysis revealed a non-random social network centered on the dominant individual. Contrary to previous research, size did not predict dominance, but it was correlated with network centrality. The factors determining dominance of lower ranks were difficult to discern, which is characteristic of despotic societies. This study provides the first heterarchical assessment of stingray sociality, and suggests this species is capable of complex social behavior. Given higher dominance and centrality relate to greater access to the provisioned resource, the observed social structure likely has fitness implications.

Food consumption of saltwater crocodile (Crocodylus Porosus) in a reptile farm of Bangladesh

An extensive study was conducted on food consumption and feeding behavior of saltwater crocodile (Crocodylus porosus) in the Reptiles Farm Ltd. (RFL) located at Hatiber village, Bhaluka, Mymensingh. The study was mainly based on direct observation and previous data collected by the technicians of the RFL. Average temperature (0C) in the farm area was significantly correlated with average food consumption (g) of the hatchlings (r = 0.714, p<0.05, n = 12). The average temperature and the average food consumption were highest in August and it was 30.5 ±5.5 0C and 45.02 ±13.05 g, respectively. Monthly feeding of hatchlings was different in three individual tubs. The highest food consumption was in August although; hatchery’s temperature was constant (320C). Crocodilians can increase their level of consumption during warmer months of the year while decreasing it in the cooler months. The highest quantity of food was given in October, probably for accumulation of fat in their body which would provide energy in the whole winter season. A total of 93.1 kg provisioned food was supplied to an adult crocodiles per year. Food consumption of crocodile is temperature dependent and the potentiality of crocodile farming is embedded in it, by considering this factor it may gain prosperity of crocodile farming in our country.Bangladesh J. Zool. 41(2): 173-179, 2013

Cooperative Breeding of the Yellow-Rumped Marshbird (Icteridae) in Argentina and Paraguay

We found helpers at eight of nine nests of Yellow-rumped Marshbirds (Pseudoleistes guirahuro) from northeastern Argentina and Paraguay. From one to four helpers were observed during the incubation and nestling periods, but during nest building we saw solitary pairs. The helpers, of unknown sex and age, provisioned food to the chicks and defended the nest against several raptors. The Yellow-rumped Marshbird had a similar breeding system to its congener the Brown-and-yellow Marshbird (P. virescens) except that the former did not nest in colonies. According to a recent molecular phylogeny both Pseudoleistes marshbirds plus the Saffron-cowled Blackbird (Xanthopsar flavus) form a well-defined clade. All three of these species have helpers. This result suggests that cooperative breeding in the Icteridae has a phylogenetic component. Cría Cooperativa de Pseudoleistes guirahuro en Argentina y Paraguay Resumen. Encontramos ayudantes en ocho de nueve nidos de Pseudoleistes guirahuro presentes encontrados en el noreste de Argentina y en Paraguay. Los ayudantes, de uno a cuatro, fueron observados en nidos durante los períodos de incubación y con pichones, pero durante la construcción del nido vimos parejas solitarias. Los ayudantes, de sexo y edad desconocidos, aportaron alimento a los pichones y defendieron el nido contra diversas aves rapaces. Pseudoleistes guirahuro tiene un sistema de cría social similar al de su congénere P. virescens, aunque no nidificó en colonias. Según la reciente filogenia molecular de la familia los dos Pseudoleistes más Xanthopsar flavus forman un clado definido, y estas tres especies tienen ayudantes. Este resultado sugiere que la presencia del sistema de cría cooperativa tiene un componente filogenético entre los ictéridos.

Provisioning by tourists affects the behaviour but not the body condition of Mareeba rock-wallabies (Petrogale mareeba)

Feeding free-ranging native animals is a form of wildlife-based tourism that is particularly popular in Australia as a result of the cryptic nature of many native species. The colony of Mareeba rock-wallabies (Petrogale mareeba) at 'Granite Gorge', North Queensland, where tourists feed a spatially defined subset of animals daily, was studied to determine the effects of provisioning on their behaviour and body condition. Provisioned P. mareeba had higher activity levels, including higher aggression levels, and spent more time performing contact behaviours (including mutual and non-mutual allogrooming) than did non-provisioned animals. Possible explanations for increased aggression include competition over provisioned food and territorial defence. Increased contact behaviours may serve to reduce tension caused by provisioning. The diurnal activities of the provisioned rock-wallabies were dictated by the activities of tourists. Provisioned rock-wallabies emerged from their shelters to receive food much earlier each afternoon than did the unprovisioned animals. The level of autogrooming exhibited by the provisioned wallabies was much higher than that of the unprovisioned animals, presumably as a thermoregulatory response to the high afternoon temperatures. Although provisioned P. mareeba feed more, their higher activity levels explain the lack of difference in the body condition between the two groups.