Great Swamp National Wildlife Refuge Research Articles

Use of Camera Traps Provides Insight into the Feeding Ecology of Red Foxes (<i>Vulpes vulpes</i>)

Red Foxes (Vulpes vulpes) often carry food items to caching sites and while making provisioning trips to litters. This behaviour provides opportunities to use camera traps to record Red Foxes carrying food that is likely prey. As part of a larger study using camera-trap surveys to monitor carnivore populations at Great Swamp National Wildlife Refuge, New Jersey, our cameras also recorded Red Foxes carrying food items allowing us to gain insight into the feeding ecology of this predator. Camera traps documented Red Foxes carrying food 71 times; items included mammals (78.9%), birds (19.7%), and fish (1.4%). Small mammals (unknown rodent or soricid species [23.9%] and voles [Microtus or Clethrionomys spp.; 5.6%]) were the most common groups of food items and Muskrat (Ondatra zibethicus; 15.5%) was the most common food item identified to species. Our surveys corroborate traditional diet assessments (e.g., scat analysis) of Red Foxes in North America, identifying them as a generalist forager that typically consumes smaller mammals. We also highlight the potential to apply camera trapping as a supplemental technique for gaining additional insight into the feeding ecology of this predator.

Camera traps at northern river otter latrines enhance carnivore detectability along riparian areas in eastern North America

We evaluated the efficacy of placing camera traps at river otter (Lontra canadensis) latrines (discrete sites in riparian areas where otters regularly deposit scats, urine, and anal secretions) to detect other carnivores occupying Great Swamp National Wildlife Refuge, New Jersey, USA. We postulated that scents at latrines may serve as an attractant to other carnivores and evaluated this premise by using camera traps to compare carnivore detection rates (overall and by species) and richness (overall and for each survey month) between latrine (n=5) and non-latrine riparian areas (n=5). On average carnivore richness was about 1.7 times higher than that of a non-latrine, and mean richness was higher at latrines for all survey months. Likewise, the overall carnivore detection frequency was 3.5 times greater at latrines, and the detection frequencies for red foxes (Vulpes vulpes), northern raccoons (Procyon lotor), river otters, mink (Neovison vison), long-tailed weasels (Mustela frenata), and Virginia opossums (Didelphis virginiana) were greater at latrines. American black bears (Ursus americanus) and eastern coyotes (Canis latrans) where detected more frequently at non-latrines. Our study provides evidence that placement of camera traps at otter latrines may serve as a new and novel approach for monitoring carnivore populations in riparian areas.

Diet of the Eastern Mudminnow (Umbra pygmaeaDeKay) from Two Geographically Distinct Populations within the North American Native Range

Umbra pygmaea (Eastern Mudminnow) is a freshwater species common in Atlantic slope coastal lowlands from southern New York to northern Florida and is typical of slow-moving, mud-bottomed, and highly vegetated streams, swamps, and small ponds. We examined its seasonal food habits at the Great Swamp National Wildlife Refuge (NWR), NJ and at the Croatan National Forest, NC. A total of 147 Eastern Mudminnow from 35–112 mm TL and 190 Eastern Mudminnow from 22–89 mm TL were examined from these sites, respectively. At both locations, we found it to be a bottom-feeding generalist that consumes cladocerans, ostracods, chironomid larvae, coleopteran larvae, and other insects and crustaceans. Ostracods were most common in the diet at the Great Swamp NWR and occurred in 62% ± 2.5% of the stomachs with food. At Croatan National Forest, chironomid larvae were most common and occurred in 66.7% ± 15.8% of the stomachs. There were no statistically significant differences in diet composition between the sites during the winter, summer, and fall. However, when compared on an annual basis, Jaccard's Index (θJ = 0.636, P = 0.05) suggested that the diet at the two study sites was significantly different. While we identified the same major food groups at both locations, the utilization of these food groups varied seasonally. Detritus was a major stomach content at both locations throughout the year. We also documented cannibalism during the summer season at both locations. The seasonal diet of the Eastern Mudminnow was similar to that of Umbra limi (Central Mudminnow) and Umbra krameri (European Mudminnow). Our findings here are the first quantitative examinations of seasonal differences in the diet of the Eastern Mudminnow within its native North American range.

Age, Growth, and Reproduction of the Eastern Mudminnow (Umbra pygmaea) at the Great Swamp National Wildlife Refuge, New Jersey

Abstract Umbra pygmaea DeKay (Eastern Mudminnow) is one of four species of Umbridae in North America. There is little published life-history information on the species within its native range, particularly on age, growth, and reproduction. This study focuses on these aspects of the life history of this fish at the Great Swamp National Wildlife Refuge in Morris County, NJ. A total of 336 fish of seven species was collected from June 1978 through May 1979, with the Eastern Mudminnow comprising 74% of the total. The average annual growth increment in total length for the Eastern Mudminnow was 15.3 ∓ 2.06 mm, with age-1 fish averaging 40 mm total length and age-5 fish, the oldest collected, averaging 107 mm total length. The length-weight relationship was log10W = -5.291 + 3.182 log10TL mm for males and log10W = -4.999 + 3.032 log10TL mm for females. We observed no statistically significant sexually dimorphic differences in length-weight relationships in this population. The ratio of females to males increase...

Use of an Artificial Nesting Mound by Wood Turtles (Glyptemys insculpta): A Tool for Turtle Conservation

Abstract We constructed an artificial nesting mound for Glyptemys insculpta (Wood Turtle) in the Great Swamp National Wildlife Refuge, NL The original nesting site was impacted by development and invasive plants. The new nesting mound was constructed from similar soil and was 100 m distant from the original site. The new mound was 50 m from stream habitat and in an old field where it received full sun for the entire day. The mound was 18 m long, 8 m wide, and had a maximum height of 1.5 m, with gently sloping sides. We encountered nest-searching female Wood Turtles on the impacted site during late May to early June for four years, 2007–2010. We carefully hand-carried females to the new nesting area and allowed them to choose whether or not to nest on the mound. We protected all nests from predators. Seventeen of 18 nests that were deposited and left on the nesting mound produced live hatchlings. Six clutches had 100% hatching success, with only one failing completely. At least nine different female Wood T...

Observations on Mammalian Prediation of Snapping Turtle Nests (Reptilia, Testudines, Chelydridae)

An investigation of the ecology of the common snapping turtle within the Great Swamp National Wildlife Refuge, Basking Ridge, New Jersey, was initiated in 1975. Observations made during three turtle nesting seasons indicated that a large number of nests fell victim to mammalian predation pressure. The study reported here was undertaken in an attempt to determine how predators locate turtle nests and to ascertain which factors may either promote or inhibit predation efficiency. Location of turtle nests may be facilitated by the predator's sighting of the female turtle during nesting or by olfactory clues associated with: (1) secretions of the nesting female; (2) the egg; or (3) disturbance of soil layers during nest digging. We were also concerned with: (1) whether predation will occur during periods other than the regular turtle nesting season; (2) whether established turtle nesting areas along watercourses experience greater predation pressure than locations not normally used for nesting; and (3) precipitation levels have any effect on predation efficiency. An informal study was conducted 8-19 April 1977 using decoy nests stocked with chicken and/or dove eggs buried to an approximate depth of 10 cm, an average derived from measurements of opened turtle nests. Results suggested that: (1) predators would readily open these nests in the absence of visual or olfactory clues associated with nesting turtles; (2) established nesting areas adjacent to watercourses were no more vulnerable to predation than areas where nests were not normally found; (3) predation pressure appeared to be as intense in mid-April as during May-June, the regular turtle nesting period; and (4) live trapping at the location of the decoy nests resulted in the capture of raccoons exclusively. As a result of this work, further studies were undertaken to confirm these findings and to elucidate the other possible parameters of predation already mentioned.

Larval Tabanidae (Diptera) of the Great Swamp, New Jersey1

Studies defining the distribution of larvae in extensive tabanid breeding habitats have been restricted mostly to salt-marsh species. The purpose of my study was to define the breeding habitats of the dominant Tabanidae of an inland swamp in north-central New Jersey and to test a method of sampling these species with emergence traps. Previously described were the 3 habitats studied, a maple swamp bed, a stream bank (“stream”), and a pond margin (“opening”) (Thompson 1969); and the physiography and vegetation of Great Swamp National Wildlife Refuge (GS) (Thompson 1967).

Feeding of Forcipomyia fairfaxensis1 on Grass Frogs (Rana spp.) in New Jersey2

On 6 afternoons from July 17 through Sept. 11, 1967, the biting midge Forcipomyia (Lasiohelea) fairfaxensis Wirth (Diptera: Ceratopogonidae) was observed feeding on the green frog, Rana clamitans Latreille, and on the grass frog, R. pipiens L., in Great Swamp National Wildlife Refuge, N. J. This report describes the circumstances of these observations, compares the behavior of F. fairfaxensis with that of the European F. velox Winnertz, and suggests a method for collecting Forcipomyia feeding on frogs.