frog population graph

Distribution of all frog sightings through the habitats of the reserve (D. granuliferus and D. auratus combined). Top: Kyle Gustafson; bottom: Robert Newman. 33, Average air temperature (˚C)36 34 32 0:00 30 2:00 4:00 Bamboo6:00 28 Secondary 8:00 10:00 Riparian12:00 Deforested meadow14:00 26 16:00 24 18:00 22 20:00 20 22:00 TimeFigure 13. In 2005, the property was donated toPitzer College and farming maintenance was abandoned. When a frog was sighted, the observerimmediately took three measurements (Figure 6): (1) The distance from the observer to the frog’s location at first sighting. not in fullsunlight). Sightings were treated as independent events (iii) by counting each frog as anindividual observation, even if frogs were within close proximity to each other. Prominent water sources are represented by blue symbols (filled polygon = pond; solid line = stream, knownlocation; dotted line = stream, estimated location [surveyed by McFarlane, 2001 {unpubl. Cryptic and 9, nocturnal, the typical frog or toad is a challenge to study in its natural environment. The research period corresponded to the Dendrobatid matingseason and the peak of their activity throughout the year (reviewed by Savage, 2002).Observing at this time guaranteed the highest number of frog sightings possible, leading toelevated estimates of population densities and an overall optimistic perspective of theDendrobatid presence on the Firestone Reserve.Population Density The population density of frogs was measured with the Hayne Estimator (Hayne,1949). Theendemic poison dart frogs of Costa Rica, however, provide a colorful alternative to studyingcryptic indicators in the tropics. Photographs by Keith Christenson.

... because an adjacent population occurs across the Ohio … Population Densities of Poison Dart Frogs in a ... Like this book? The densities recorded in the secondary and bamboo habitats were too low to detect astatistically significant difference between these habitats. Where multiple frogs were seen in the same location, sighting frequencies aresymbolized by graduated circles (see legend).

Finally, thanks to my family and friends for theirencouragement through all. full sunlight). 14:185-204.Basset, Y., H. Alberlenc, H. Barrios, G. Curletti, J. Berenger, J. Vesco, P. Causse, A. Haug, A. Hennion, L. Lesobre, F. Marques, and R. O’Meara. The proximity of each sighting to water was determined using COMPASS software(Version 5.05; Fish, 2005) The straight-line distance between each sighting location and theclosest water source was measured and then correlated to the number of frogs sighted at thelocation using a linear regression calculated with VassarStats (Lowry, 2007).Abiotic Factors To determine whether the transect distribution proportionally represented the amountof water in each habitat, an analysis of transect-resource proportionality was conducted usingmeasurements from the Firestone maps created with ArcGIS to compare the ratio of thehabitat area within 50 m of a water source to the total habitat area versus the transect length(by habitat) to the total transect length (by habitat). While both species areabundant on the Firestone Reserve, D. granuliferus is internationally recognized as athreatened species due to habitat loss and degradation as well as human harvesting of thespecies (IUCN, 2006).

Future studies could evaluate similar parameters in otherpoison dart frog species to expand our understanding of the sensitivity of this group to habitatdestruction.

Extensive research indicates that most frog speciesincrease activity during periods of rainfall (Aichinger, 1987; Duellman, 1995; Gottsbergerand Gruber, 2004). 60Number of transects with frogs observed 50 40 30 20 10 0 Absent Present Rainfall status at time of observationFigure 12.

Loggers were set to record data foreach day and night of the study period and measured the habitat temperature every 5 or 20minutes, depending on the format available on the logger. Like many other countries throughout the world, Costa Rica has been the site oframpant deforestation over the past few centuries. The study species: Dendrobates granuliferus (top) and Dendrobates auratus(bottom). Species composition and invasion in Argentinean secondary forests: Effects of land use history, environment and landscape.

With increasing job opportunities in the urban-based tourism and textile industries, workers have begun to migrate away from agriculturalareas (Aide and Grau, 2004). Mean daily temperature fluctuations in each study habitat and controlenvironment (deforested meadow).Time of day To evaluate overall trends in frog sighting frequency, data from both species werecombined and compared to the time of sighting (Figure 14). If the difference in frog densities increases between thesetwo habitats with a greater sample size, then bamboo should be further explored as asustainable crop in Costa Rica. The breeding intensity, that is the number of female wood frogs (or the number of egg masses) detected in each wetland, was highly variable (see graph at upper right). Water sources (streams andponds) were approximated and drawn by hand according to the trail survey (McFarlane,2001, unpubl. At each of the 174 wetlands surveyed, Dr. Newman and his assistant recorded the wetland location using a GPS receiver (satellite-based global positioning system). Since breeding pairs of D. granuliferus and D. auratusonly come into contact for a short period during courting and amplexus (Dunn, 1941;Summers et al., 1999), mating was not believed to substantially impact overall frogdistribution during the study. My data, however, indicate a strong correlationbetween the number of sightings and the proximity to a permanent water source (Figure 9).Other observations of poison dart frogs aggregating near large water sources have not beenpreviously documented in published literature. Transects 1 and 4 couldnot be shuffled because they provided starting and ending access or connected path loops,respectively.Table 1. Because many of the human impacts thatthreaten D. granuliferus and D. auratus also affect other tropical amphibians and potentiallyother groups of organisms, these two species serve well as indicators of the status of tropicalwildlife populations. Each observation followed the same protocol. (ii) Animals on the transect line are observed with a probability of one. The reserve has aunique history that makes the area a suitable research site for an examination of poison dartfrog populations in regenerating habitats. In 2001, Pitzer College acquired the Firestone Center, a parcel of land in Costa Ricathat had previously been selectively stripped of forest and converted into a cattle farm and Figure 2.

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