AnAge entry for Didelphis aurita. Classification (HAGRID: ). Taxonomy Genus: Didelphis; Species: Didelphis aurita; Common name: Big-eared opossum . Didelphis aurita was long considered a subspecies of Didelphis marsupialis, however recent DNA evidence places Didelphis aurita as its own species. Parasitol Res. Jan;(1) doi: /s Epub Dec 1. Identification of opossums Didelphis aurita (Wied-Neuweid, ).
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Nine-year demography of the black-eared opossum Didelphis aurita Didelphimorphia: Didelphidae using life tables. Demografia do marsupial Didelphis aurita Didelphimorphia: A population of the black-eared opossum, Didelphis aurita Wied-Neuwiedwas studied during by capture-mark-recapture in the Atlantic Forest in the state of Aurit de Janeiro. Cohorts were established with females marked still in the pouch, classified into five age classes.
Population parameters were estimated using life tables. Fecundity was inversely correlated with survival, reproductive value was inversely correlated with mortality and residual reproductive value was inversely correlated with fecundity. The intrinsic rate of increase was always close to zero and tended to be slightly negative.
The black-eared opossum can be considered a good model species for this type of study.
Atlantic forest; cohort; intrinsic factors; small mammals; survival. A taxa de fecundidade foi inversamente correlacionada com a sobrevida, o valor reprodutivo inversamente correlacionado com a mortalidade e o valor reprodutivo residual inversamente correlacionado com a taxa de fecundidade. Demographic studies are important to understand factors that influence population ecology as well as for planning conservation and management strategies SCHWARTZ et al. These studies also permit a better understanding and analysis of tradeoff relationships, such as between survival and fecundity STEARNS These details are fundamental for understanding life-history strategies, ecology and persistence of populations.
Management programs require these kinds of data, especially long-term data, even for wildlife species that are not endangered. Life table use permits the estimation of age-specific parameters of the population of interest, such as mortality, fecundity and reproductive value. Captures may include only females, under the assumption that all females are available for fertilization by the males, since reproduction, and thus demographic data, comes from the females STEARNS However, to obtain the demographic parameters, females from all age classes need to be captured.
For example, negative correlations are often found in mammalian populations between survival and fecundity or between mortality and reproductive value. Occasionally arboreal, this mostly terrestrial, generalist species is found in all habitat types of the Atlantic Forest, as well as urban and rural areas and may often be dominant among small mammals CERQUEIRA et al.
The population dynamics of D. The objective of this study was to carry out a nine-year demographic analysis of D.
Specifically, we wished to test the following hypotheses: This would be the case, if there is a cost to reproduction, such that a large current reproductive effort reduces future reproductive value more than a small current reproductive effort ZAMMUTO The grids vary in distance from the highway: Despite it being a national park, the forest in the study area suffers from a variety of human disturbances, such as dirt roads and cottages.
During the study, the greatest average maximum temperature was Total monthly rainfall varied from a minimum of 0. Animals were captured in the three grids during five days every other month between April April Traps 25 stations per grid were placed every 20 m total area 0. Oats, banana, peanut butter and bacon were used as bait. Upon capture, the location and date were recorded, along with measures of body mass, body size, tail length, reproductive condition and teeth eruption and functionality pattern following GENTILE et al.
Didelphis aurita – Wikipedia, la enciclopedia libre
Females videlphis used for life table construction and only females that were marked while young and still within the pouch were used, comprising eight cohorts: Each cohort began in August, the month when females began to be captured with young in the pouch see results.
The cohort was not analyzed because many were still alive. Animals were included in the analysis until disappearing from the study auriita. Females were classified into five age classes. Thus, age classes of similar time intervals were established, based on teeth and development characters: Hypotheses were tested using Spearman Correlation Statistica 6. Fifty six litters were marked and monitored during this divelphis.
The maximum of 12 litters per year was observed in and the minimum of three litters in Of these, females were captured, 27 of which were recaptured after weaning and nine of which lived for more than 16 months Tab. The longest lived individual survived days 20 months. In the cohort, not a single individual marked in the pouch was recaptured and in only one individual was recaptured after weaning. Thus, it was not possible to establish life tables for these two cohorts.
The proportion of females recaptured after weaning l x was small didelphus all cohorts Tab. All cohorts showed an accentuated decrease in l between first and second age classes, i. Survival also declined after ridelphis second age class, but with less intensity Fig. Similarly, survival rate p x was greatest for the second age class and mortality d x in didelphi first age class Tab. In most cohorts, adult survival was 1. Mortality rate q x was highest in lactant and young, while lowest values were found for adults in most cohorts, since adults were also captured as senescent Fig.
Young had the greatest life expectancy values e xfollowed by subadults Fig. After this class, life expectancy declined. The first females with young in the pouch were captured in August and by February end of reproductive periodmost aurjta were still lactating, but without young in the pouch.
Females began to breed at approximately 5 months days of age. Average litter size was 7. Sex ratio in the pouch was 1: The cohort was the largest, with five litters l. Females from these cohorts produced one litter per season, except for two females, that each had two litters during one breeding season.
Fecundity rate increased from subadults to adults, where it reached its maximum Fig. In theevidence of reproduction was only found in the senescent age class, therefore fecundity rate was zero in all other age classes.
Fecundity rate in the and cohorts for the senescent class was zero. Fecundity could not be estimated for the cohort because the only female in reproductive age showed no signs of reproduction. Reproductive value increased to the third or fourth age classes, after which it declined Fig.
The greatest residual reproductive values were those of young and subadults Fig. Mortality was negatively correlated with reproductive value, supporting the third hypothesis that high mortality rates reduce the contribution to future generations.
The cohort was apparently atypical due to small population size, high survival and low mortality, and fecundity rates. In this cohort, only senescent females reproduced, so reproductive value was constant in the last three age classes Fig. Generation time G c varied from Only one female, born in Augustreproduced at the end of the same breeding season in which she was born January Overall generation time was The intrinsic rate of increase, r 0was close to, and usually somewhat less than zero, suggesting a population decline Tab.
The intrinsic rate of increase r 0 varied between Also, the net reproductive rate R 0 tended to values below 1. The large sample size required for use of life tables is often the major hurdle against their use.
Individuals must be followed from birth to death, which can be difficult. The opossum can be considered a good mammalian model for the use of life tables, because of its large population size, especially in disturbed areas and around dwellings, ease of capture and ability to capture and mark young in the pouch. The survival and mortality curves suggest that the opossum has a type III survival curve due to the accentuated decline in survival after the first age class PEARL A second possibility is related to the reproductive strategy of marsupials, with little investment in gestation and a large investment in lactation.
The loss of young at the beginning of lactation should be common, since until this time, the investment of the female was low, also resulting in a type III curve.
As a consequence, the life expectancy increases after the young age class and then declines throughout life. High post-weaning mortality is apparently best explained by vulnerability of the recently weaned young. Generation time for the cohort was atypical and almost as twice as high compared to the preceding and following years.
Perhaps this was an artifact of finding no reproductive females during this year, except among the senescent class. Since birth dates vary along the season and litters may be produced at the beginning or end of the breeding season, this will influence the generation time among cohorts. And, generation time of one cohort can influence that of subsequent cohorts.
This is one of the reasons for the need of longterm studies. Few adults survived from one breeding season to the next and turnover rates were high each year. This was most evident in the cohort, where not a single young produced came from a female of the preceding cohort. The new individuals that formed that cohort had to come outside the study area. Spatial dynamics among females not studied here may be an important component in the population turnover each year.
In the case of D. A strong correlation between leaf litter production and opossum population dynamics was found in a previous study in the same location as this study GENTILE et al. The decline in reproductive value at the senescent age class is due to the increased mortality at that time. Thus, senescent females will contribute less to future generations than adult females.
The negative relationship between fecundity rate and survival supports the hypothesis that an increasing cost of reproduction in an age class reduces survival in the same and subsequent age classes, due to the stress that reproduction induces ZAMUTTOCASWELL Basic understanding of mammalian demography in tropical forests like the Atlantic Forest requires the study of common and dominant species, such as D.
In fragmented forest areas, specifically where large predators are absent, species of Didelphis tend to increase in abundance. Population monitoring and demographic analyses of Didelphis may be of fundamental importance to understand community structure, especially in disturbed areas, where they may reach very large population sizes.