ABSTRACT Conservation of a target species is often hindered by the absence of basic demographic i... more ABSTRACT Conservation of a target species is often hindered by the absence of basic demographic information. Lithobates [Rana] okaloosae (Florida Bog Frog) was discovered in 1982 and occupies only three counties in northwest Florida, with its geographic range occurring almost exclusively on Eglin Air Force Base. This limited distribution has led to the listing of the Florida Bog Frog as a species of special concern in Florida. We used a mark-recapture approach to 1) estimate population sizes and densities of male Florida Bog Frogs at four sites; 2) estimate recapture rates of males among sites, within years, and be-tween years; 3) examine the relationship between male body condition and residency time in breeding sites; and 4) examine the variation in male body condition across sites. Florida Bog Frog population sizes and densities differed among sites, but not across years. Recapture rates were high within a breeding season but low between years, suggesting that males have high site fidelity and survival rates during the breeding season, but that annual mortality or dispersal rates are high. Lastly, body condition of males did not differ across sites or affect residency time during the breeding season. Understanding basic demographics of this spe-cies will aid future conservation efforts and management decisions.
Rates of brood parasitism by Brown-headed Cowbirds Molothrus ater on nests of Brown Thrashers Tox... more Rates of brood parasitism by Brown-headed Cowbirds Molothrus ater on nests of Brown Thrashers Toxostoma rufum in south-central North Dakota ranged from 3% to 18% from 1984-1986. The average observed rate of parasitism, 12%, was higher than typically reported for Brown Thrashers. We conducted an experiment to determine if these high observed rates of parasitism were a result of unusually high rates of parasitism by cowbirds or unusually low rates of rejection by thrashers. Brown Thrashers removed 58% of experimentally-placed cowbird eggs. This rate of rejection is significantly lower than that previously reported for Brown Thrashers and for other rejector species. We conclude that thrashers in this area are parasitized at a high rate, but that low rates of rejection are at least partially responsible for the high observed rate of parasitism. These results suggest that the classification of Brown Thrashers as a rejector species should be reevaluated and that further study of geographic variation in cowbird host behavior and the role of learning in egg recognition is warranted.
... Shannon M. Knapp ,† ,; Carola A. Haas,; Douglas N. Harpole ,‡ ,; Roy L. Kirkpatrick. ... We e... more ... Shannon M. Knapp ,† ,; Carola A. Haas,; Douglas N. Harpole ,‡ ,; Roy L. Kirkpatrick. ... We established five sites ( Blacksburg 1, Blacksburg 2, West Virginia 1, West Virginia 2, and Clinch ) in the Appalachian Mountains of southwestern Virginia and West Virginia. ...
Abstract Although investigators have determined that some anurans can influence nutrient availabi... more Abstract Although investigators have determined that some anurans can influence nutrient availability in terrestrial systems, ecological interactions among salamanders, invertebrates, and leaf litter decomposition in the detrital ecosystem are poorly understood. We examined the effects of the Eastern Red-Backed Salamander (Plethodon cinereus) on leaf litter decomposition rates and invertebrate populations in the mixed oak forests of southwestern Virginia from May 2006 to June 2008. We constructed 12 in situ mesocosms with 0, 1.0, or 2.0 P. cinereus/m2 (4.0 P. cinereus/m2 in year 2). We quantified decomposition rates of leaf litter and numbers of invertebrates with litter bags that were removed from mesocosms monthly throughout the experiment. Further, we assessed what taxa of invertebrates were preyed upon by salamanders with gastric lavage. Across our 2-year experiment, we were unable to detect an effect of salamander abundance on rates of leaf litter decomposition, numbers of broad invertebrate taxonomic groupings, or functional guilds of invertebrates. Stomach analysis confirmed that salamanders were euryphagic, but they consumed more herbivores than detritivores or predators. Although we are unclear why these results conflict with earlier work indicating that salamanders can influence invertebrates and leaf litter decomposition, variability of canopy trees or microclimate may have contributed to a lack of control of invertebrate populations or litter decomposition by salamanders in the complex mixed-oak forests of the Appalachian Mountains.
ABSTRACT Conservation of a target species is often hindered by the absence of basic demographic i... more ABSTRACT Conservation of a target species is often hindered by the absence of basic demographic information. Lithobates [Rana] okaloosae (Florida Bog Frog) was discovered in 1982 and occupies only three counties in northwest Florida, with its geographic range occurring almost exclusively on Eglin Air Force Base. This limited distribution has led to the listing of the Florida Bog Frog as a species of special concern in Florida. We used a mark-recapture approach to 1) estimate population sizes and densities of male Florida Bog Frogs at four sites; 2) estimate recapture rates of males among sites, within years, and be-tween years; 3) examine the relationship between male body condition and residency time in breeding sites; and 4) examine the variation in male body condition across sites. Florida Bog Frog population sizes and densities differed among sites, but not across years. Recapture rates were high within a breeding season but low between years, suggesting that males have high site fidelity and survival rates during the breeding season, but that annual mortality or dispersal rates are high. Lastly, body condition of males did not differ across sites or affect residency time during the breeding season. Understanding basic demographics of this spe-cies will aid future conservation efforts and management decisions.
Rates of brood parasitism by Brown-headed Cowbirds Molothrus ater on nests of Brown Thrashers Tox... more Rates of brood parasitism by Brown-headed Cowbirds Molothrus ater on nests of Brown Thrashers Toxostoma rufum in south-central North Dakota ranged from 3% to 18% from 1984-1986. The average observed rate of parasitism, 12%, was higher than typically reported for Brown Thrashers. We conducted an experiment to determine if these high observed rates of parasitism were a result of unusually high rates of parasitism by cowbirds or unusually low rates of rejection by thrashers. Brown Thrashers removed 58% of experimentally-placed cowbird eggs. This rate of rejection is significantly lower than that previously reported for Brown Thrashers and for other rejector species. We conclude that thrashers in this area are parasitized at a high rate, but that low rates of rejection are at least partially responsible for the high observed rate of parasitism. These results suggest that the classification of Brown Thrashers as a rejector species should be reevaluated and that further study of geographic variation in cowbird host behavior and the role of learning in egg recognition is warranted.
... Shannon M. Knapp ,† ,; Carola A. Haas,; Douglas N. Harpole ,‡ ,; Roy L. Kirkpatrick. ... We e... more ... Shannon M. Knapp ,† ,; Carola A. Haas,; Douglas N. Harpole ,‡ ,; Roy L. Kirkpatrick. ... We established five sites ( Blacksburg 1, Blacksburg 2, West Virginia 1, West Virginia 2, and Clinch ) in the Appalachian Mountains of southwestern Virginia and West Virginia. ...
Abstract Although investigators have determined that some anurans can influence nutrient availabi... more Abstract Although investigators have determined that some anurans can influence nutrient availability in terrestrial systems, ecological interactions among salamanders, invertebrates, and leaf litter decomposition in the detrital ecosystem are poorly understood. We examined the effects of the Eastern Red-Backed Salamander (Plethodon cinereus) on leaf litter decomposition rates and invertebrate populations in the mixed oak forests of southwestern Virginia from May 2006 to June 2008. We constructed 12 in situ mesocosms with 0, 1.0, or 2.0 P. cinereus/m2 (4.0 P. cinereus/m2 in year 2). We quantified decomposition rates of leaf litter and numbers of invertebrates with litter bags that were removed from mesocosms monthly throughout the experiment. Further, we assessed what taxa of invertebrates were preyed upon by salamanders with gastric lavage. Across our 2-year experiment, we were unable to detect an effect of salamander abundance on rates of leaf litter decomposition, numbers of broad invertebrate taxonomic groupings, or functional guilds of invertebrates. Stomach analysis confirmed that salamanders were euryphagic, but they consumed more herbivores than detritivores or predators. Although we are unclear why these results conflict with earlier work indicating that salamanders can influence invertebrates and leaf litter decomposition, variability of canopy trees or microclimate may have contributed to a lack of control of invertebrate populations or litter decomposition by salamanders in the complex mixed-oak forests of the Appalachian Mountains.
Uploads
Papers by Carola Haas