Transcript Precipitation Dependent Reproductive Patterns of

Precipitation Dependent Reproductive Patterns
of Brazilian Pantanal Anuran Species
Janet Buckner1, Dr. Vanda Ferreira2
1
Department of Biological Science, SUNY Oswego, Oswego, New York , Universidade
2
Federal de Mato Grosso do Sul, Campo Grande, Brazil
Introduction
Phenologists study patterns in the lives of organisms
which are initiated by or correlated with climate patterns.
This knowledge is important to understand the
requirements of various species for vital life functions. In
recent times, phenology can help us to understand the
consequences of major changes on Earth for species
including global warming. In relation to phenology, many
animal species employ reproductive strategies which are
weather dependent. In this study we test the validity of
this observation in species of anurans in the Brazilian
Pantanal by comparing precipitation data from the period
2005-2006 with anuran survey data from those years.
We believe there exists a correlation between
precipitation and anuran reproduction and age of
individuals in this area.
Objectives
1.
2.
3.
4.
5.
To describe the phenology of amphibians.
To organize anuran population data into the
categories adult, sub-adult and juvenile.
Determine possible temporal population patterns
among these age ranges .
To determine if a correlation between rainfall and
reproduction exists in various anuran species.
Determine if those correlations hold only for certain
reproductive strategies.
Methods
Data collection – the study was conducted in the Brazilian
Pantanal in the state of Mato Grosso do Sul at various
locations within Fazenda Nhumirim. Anurans were surveyed
during the years 2005 to 2006 using pitfall traps (see Figure
1). These traps were opened and checked daily over nine
approximately week long intervals. Specimens were
collected from the traps and the following measurement s
taken daily: species, sex, age, length and weight (Figure 2).
Determinations – sex was determined by the presence of
sexually dimorphic traits when applicable. This was usually
not possible for juveniles who were not yet sexually mature.
Age was determined by CRA (the length of the animal from
snout to cloaca) parameters published in Prado and Haddad
2005. For the species Leptodactylus chaquensis, reliable
data on the size of adult individuals was not available so the
average of the sizes of known adults from our own data
were used to verify ages of all individuals of this species.
For Physalaemus albonotatus, the smallest recorded size for
adult males within our data was used to determine the age
for those animals with undetermined ages. Animals
between eighteen and 23.5 centimeters were excluded if sex
could not be determined.
Figure 1. The set-up for a pitfall trap used to
collect specimen.
Figure 2. Students taking measurements of
captured specimen.
Results
Based on the data presented here it seems plausible that the reproductive patterns of the following species are dependent upon or closely correlated with precipitation.
Conclusion
It seems that there is a delayed response in the abundance
of juveniles in relation to precipitation. However, this is
expected if we consider that the adults are triggered to lay
eggs at the time of the rain, it will take some time for those
eggs to metamorphose into juvenile frogs. Since we used
the juvenile populations to make the graphs, we should
expect a time lapse between rainfall and peaks in juvenile
frog population. To confirm a positive correlation between
precipitation and reproduction, though, statistical analyses
will be necessary as well as additional years of data. A
software is being developed to identify the best associations
between rainfall and abundance of juveniles considering the
biological attributes of each species and finally to infer the
rainy season which led to the spawning of the species.
Acknowledgements
References
Thome, M.T.C, Brasileiro, C.A. 2007. Dimorfismo sexual, uuso do ambiente e
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