Frog Diversity in Various Habitats of Iracambi 

Stephanie Rog

INTRODUCTION

• Brazil boasts 731 amphibian species, the largest number in the world, of which 467 are endemic. In some ecosystems they are the most abundant vertebrates (Blaunstein et al. 1994) and so their absence can have consequences for the entire ecological community.
• Frogs are considered to be particularly vulnerable to habitat change and good indicators of habitat quality due to their permeable skins, dual life mode and limited dispersal capabilities.
• A decline in frog populations was first reported by herpetologists in the late 1970's (Barinaga 1990, Bury 1999) and appeared to be occurring on a global scale. Alarmingly, frogs have reportedly disappeared from pristine areas or areas presumed to be undisturbed by human interference (Carey et al. 2001).
• Understanding factors that determine amphibian species distributions allows informed decisions to be made in conservation, increases our understanding of how land management impacts on amphibian species and therefore contributes towards understanding amphibian decline and rarity on a wider scale.

OBJECTIVE

To complete a pioneering survey of the diversity of frog species at Iracambi, and to study their habitat preferences. The specific objectives were:

1. Determine the different land uses at Iracambi Describe the research areas using IUCN criteria (vegetation, disturbance etc.) Collect water samples in research areas to analyze and draw conclusions regarding habitat health Record all frog species found in the different research areas, along with information on microhabitat, and climate
2. Record frog calls and build a database combining sounds, pictures and biological information

The hypotheses tested were:

• Frog diversity would be the highest within twenty-five meters of a water source and with little disturbance from human activities
• The most species and highest abundance would be found during rainfall

METHODOLOGY

Nine study sites were selected that represented all of the different land use types occurring at Iracambi. These included Eucalyptus plantations, sugar cane fields, secondary forest, artificial and temporary pools, and pasture. This study was carried out between the 25 th of October 2004 and the 26 th of February 2005. Collection occurred daily between 2000 and 2200 in all types of weather. Frogs were detected by using visual encounter and/or acoustic survey techniques (standardized transect sampling). Information recorded included a location of the species (recorded using GPS), microhabitat, abundance of species (by counting calls), climate information including precipitation and cloud cover, a digital picture and a vocalization recording.

After hearing or observing a frog, a picture was taken and then the researcher attempted to net a specimen for identification. Live specimens were used whenever possible to identify the species, but if capture was not possible, then the picture or the sound recordings were used as a secondary identification method.

Frog species of Iracambi Scientific name 1 Bufo 2 Elachtistocheis ovalis 3 Eleutherodactylus binota 4 Eleutherodactylus sp. 5 Hyla albomarginata 6 Hyla albopunctata 7 Hyla crepitans 8 Hyla faber 9 Hyla leucophyllata 10 Hyla minuta 11 Hyla pardalis juv. 12 Hyla saborni 13 Leptodactylus ocellatus 14 Phyllomedusa burmeisteri 15 Physalaemus curveiri 16 Scinax euridice 17 Scinax perereca 18 Scinax fuscovarious 19 Scinax cf. Berthae 20 Scinax cuspidatus 21 Hyla semilineata 22 Hyalinobatrachium

RESULTS Twenty-two different species were found over a period of forty-five days. The most popular habitat site was a shallow temporary pool with smooth edges, covered with reeds, grass and a few trees. There was no visible disturbance by humans and three of the species were endemic to this area. The Eucalyptus plantation and a shallow temporary pool with a high aquatic iron concentration did not support any frog species, and the sugar cane field only supported one. Temperature had no effect on thirteen species, and weather seemed to have no effect on all of the species except Phyllomedusa burmeisteri, which was only observed on clear nights with no precipitation. The most common species were Scinax euridice, Scinax cf Berthae, Hyla minuta and Hyla punctata, which were observed almost every night. The rarest species were Hyla pardalis, Physalaemus curveiri and Scinax sp. which were only encountered once. Water sampling results indicated that the iron concentration was high in a majority of the samples, but the pH, nitrate and turbidity levels were all acceptable except in sample 2, which corresponds to the area where no species were found.   Water Samples Number 1 2 3 4 5 6 7 Units Colour * 83 16 13 9 18 37 U.C Iron 22,3 4,3 0,35 0,65 0,53 0,18 2,9 mg/L Fe Nitrate 4,5 1,4 1,3 1,6 <1,0 1 1,7 mg/L NO 3 Ph 6,56 6,16 6,21 7,05 6,43 6,98 5,99 Turbidity * 27 5 3 2 5 11 N.T.U

DISCUSSION

This initial survey of Iracambi's frog population is by no means exhaustive but provides the organization and future researchers with a platform from which to conduct further research. The frog species occurrence in relation to weather and temperature was not scientifically valuable because some species were rarely encountered. Frogs are highly secretive in their habits and may spend their entire lives underground or on inaccessible mountain slopes. Their activities are highly seasonal and in tropical species, breeding may occur over an extended period of time. Future research should once again focus on the breeding season. Changes in the ecosystem are first noticed by amphibians, thus by monitoring frog populations these changes can be detected at an early stage. This is one way for humans to monitor the effects of their activities and prevent future problems.

REFERENCES

Barinaga, M. (1990) Where have all the Froggies gone? Science , 247 , 1033 – 1034 Bury, R.B. (1999). A historical perspective and critique of the declining amphibian crisis. Wildlife Society Bulletin , 27 , 1064-1068.

Carey, C., Heyer, R. Wilkinson, J., Alford, R., Arntzen, J., Halliday, T., Hungerfod, L., Lips, K., Middleton, E., Orchard, S. & Rand, A. (2001) Amphibian declines and environmental change: use of remote sensing data to identify environmental correlates. Conservation Biology , 15 , 903-913.