8 research outputs found
A retrospective cohort study in patients with tractional diseases of the vitreomacular interface (ReCoVit)
Reproductive characteristics of captive greater rhea (Rhea americana) males reared in the state of São Paulo, Brazil
Rheas (Rhea americana) belongs to the ratite group. Considering the commercial significance of this birds, some techniques, such as semen collection, were standardized. In this study, 107 male rheas (3 to 4 years of age) reared in commercial farms in the state of São Paulo, Brazil, were used. Semen was collected during the breeding and off-breeding seasons of 2001, 2002, and 2003. Bird hierarchical behavior was observed. Birds were restrained performed using a box and a black hood. Semen was collected by digital pressure on the base of the phallus, which size was measured, and the presence or absence of spiral shape was observed. Immediately after collection, semen samples were evaluated for volume, motility, sperm concentration, and morphology. In a limited number of birds, blood samples were collected to measure testosterone levels. Among the 69 birds studied during the breeding season, 44 presented large phalluses, out of which 26 showed spiral shape. The method of semen collection was efficient. The following semen parameter results were obtained: volume (0.68 ±0.14 ml), motility (61.11±11.54%), sperm concentration (3.29±1.33 x10(9) sptz/ml), and number of spermatozoa per ejaculate (2.40±1.38x10(9) sptz/ml). Morphological abnormalities were analyzed and recorded. Testosterone levels were statistically different (p = 0.0161) between the breeding and non-breeding season (53.28±18.41 ng/ml and 5:57±3.81 ng/ml, respectively). Variations in phallus size were also found between the breeding and non-breeding seasons. Larger phalluses and higher testosterone levels were correlated with dominant behavior. The results of the present experiment confirmed that it is possible to collect semen from rheas, allowing the future use of biotechnologies such as artificial insemination
Failure of captive-born greater rheas (Rhea americana, Rheidae, Aves) to discriminate between predator and nonpredator models
The capacity to recognize and respond to predators
can be lost by captive animals. Habituation to humans
caused by the captive environment can be transferred to
other stimuli, such as predators, a situation that conservation
biologists wish to avoid. Greater rheas are threatened South
American birds, for which there are plans for reintroduction
programs in Brazil. The goal of this study was to evaluate
the behavioral responses of captive-born greater rheas to
different models of predators and nonpredators. Seventeen
captive-born greater rheas, divided into four groups, from
the Belo Horizonte Zoo, Brazil were studied. Three predator
and three nonpredator models were presented to the birds
and their behavioral responses recorded. Predators versus
nonpredator models and the behavior of rheas in three
experimental phases (baseline, models, and postmodels)
were analyzed. Captive-born greater rheas modified their
behaviors in the presence of both predator/nonpredator
models, increasing alert and wary behaviors (alert, observing,
and pacing behaviors: P<0.01), showing some degree
of antipredator behavior persistence, but they were unable to
discriminate between predator and nonpredator models (all
behaviors: P>0.05). In conclusion, antipredator training
should be implemented to develop the expression of this
behavior before reintroductions are attempted
Benefits of large broods by higher chick survival and better territories in a precocial shorebird
When reproductive success is constant in one breeding phase, different tactics that increase variation in reproductive success among individuals may evolve in other phases. For instance, in shorebirds, which usually have a limited clutch size of four eggs, variation in reproductive tactics among individuals is expected either before egg-laying (e.g. diverse mating systems) or after hatching of the young (e.g. diverse parental care). In this paper, I studied the pied avocet (Recurvirostra avosetta), a shorebird with a modal clutch size of four eggs, to test whether post-hatch chick adoption as an alternative tactic can be linked to increased variation in annual reproductive success. When predation was high, naturally adopting pairs produced more filial fledglings than did pairs not adopting chicks and not losing chicks to adoption. The number of filial fledglings increased with the number of adopted young, possibly through diluting the chances of predation on filial young. Experimental chick addition did not lead to more fledged young due to low brood integrity as shown by the frequent loss of chicks from some experimental broods. When predation was low, larger broods occupied feeding territories with higher prey abundance than smaller broods, possibly due to their dominance over smaller ones. Pairs that lost chicks to adoption (donors) fledged as many filial young in their broods as did non-adopters/non-donors, whereas the total number of donors' filial fledglings, including those raised in adopting broods, approached that of adopters. These findings show, for the first time, that post-hatch alternative reproductive tactics can lead to variation in annual reproductive success and to higher success for some pairs even in species where past adaptations limit variation in reproductive success in a certain phase of reproduction