White River National Wildlife Refuge Research Articles

Pattern of space use by female black bears in the White River National Wildlife Refuge, Arkansas, USA

The manner in which space is used by animals may influence several aspects of biology, including the pattern of resource use and intra-specific competition. We monitored 16 radio-collared female black bears ( Ursus americanus) for 9,216 radio days during 1993–1995 in the White River National Wildlife Refuge (WRNWR), Arkansas, U.S.A. to investigate space use patterns. Annual home ranges (95% convex polygon) ranged from 2.10 to 11.34 km 2 with a mean (± SD) size of 4.90 (± 2.09) km 2 (n = 16). Largest home ranges were occupied by 2 females with yearlings during one year of study. Home ranges among neighbouring bears overlapped considerably. Although bears maintained larger home ranges during summer, the size of home range did not differ among seasons ( P > 0.50). Our estimates of home range size for female black bears were smaller than those obtained in a study of the same population during 1979–1982. Because the size of the bear population at WRNWR was substantially smaller (about 130 bears) during 1979–1982 compared to the present population of ≥348 bears, these results suggested that population density and size of female black bear home ranges may be negatively correlated. Conservation implications of density-dependent space use pattern are also discussed.

Subspecific affinity of black bears in the White River National Wildlife Refuge.

The black bear population of the White River National Wildlife Refuge (NWR) is adjacent to populations of black bear in Louisiana (Urusus americanus luteolus) which are listed as threatened under the U.S. Endangered Species Act. Wildlife management plans can pose restrictions on bear harvests and timber extraction; therefore the management plan for the White River NWR is sensitive to subspecific classification of its bear population. The objective of this study was to analyze genetic variation in the White River NWR and seven adjacent populations of black bears to assess the subspecific affinity of the White River NWR population. Here we report the variation at seven microsatellite DNA loci among eight black bear populations. The patterns of genetic variation gave strong support for distinguishing a southern group of black bears comprised of the White River, Arkansas; Tensas River, Louisiana; Upper Atchafalaya, Louisiana; Lower Atchafalaya, Louisiana; and Alabama/Mississippi populations. Phylogenetic analysis of individual variation suggested that historical black bear introductions into Arkansas and Louisiana affected gene pools of certain southern receiving populations, but did not significantly change interpopulation relatedness. Phylogenetic inferences at both the population and individual levels support the hypothesis that the White River NWR population of black bears belongs to the U. a. luteolus subspecies.

Estimating forest crown area removed by selection cutting: a linked regression-GIS approach based on stump diameters

The purpose of this research was to develop a model that could be used to provide a spatial representation of uneven-aged silvicultural treatments on forest crown area. We began by developing species-specific linear regression equations relating tree DBH to crown area for eight bottomland tree species at White River National Wildlife Refuge, Arkansas, USA. The relationships were highly significant for all species, with coefficients of determination ( r 2) ranging from 0.37 for Ulmus crassifolia to nearly 0.80 for Quercus nuttallii and Taxodium distichum. We next located and measured the diameters of more than 4000 stumps from a single tree–group selection timber harvest. Stump locations were recorded with respect to an established grid point system and entered into a Geographic Information System (ARC/INFO). The area occupied by the crown of each logged individual was then estimated by using the stump dimensions (adjusted to DBHs) and the regression equations relating tree DBH to crown area. Our model projected that the selection cuts removed roughly 300 m 2 of basal area from the logged sites resulting in the loss of ≈55 000 m 2 of crown area. The model developed in this research represents a tool that can be used in conjunction with remote sensing applications to assist in forest inventory and management, as well as to estimate the impacts of selective timber harvest on wildlife.

Denning Ecology of Black Bears in the White River National Wildlife Refuge, Arkansas

Lack of adequate den sites may adversely affect cub survival and reproductive success in black bears (Ursus americanus). Management of remnant bear populations in the lower Mississippi floodplain necessitates understanding denning ecology. We monitored 23 radiotagged black bears for 33 den years from 1993 to 1995 in White River National Wildlife Refuge, Arkansas to investigate denning chronology and den requirements. Bears entered dens between 1 January-20 February and emerged between 12 March-28 April. Mean (±SE) denning duration was 92.9 ± 6.6 days and varied between sex-age classes (P = 0.002). Pregnant females denned longer (117.8 ± 5.2 days, P = 0.029) than males and non-pregnant females (84.2 ± 7.7 days). More than 44% of the bears that denned (n = 27) used >1 den during a denning season, and one female used 4 dens. Most (90.2%, n = 51) dens were elevated tree cavities with a hollow opening on the top or middle of the main trunk. Three species of trees were used with 77.8% (n = 46) being overcup oak (Quercus lyrata). Basal area of trees ≥10 cm diameter at breast height (dbh; P < 0.001) and number of stems ≥84 cm dbh (P < 0.001; the min. dbh of den trees documented in this study) differed among vegetation plots with and without den trees. For seasonally flooded habitats, our results suggest the need for maintenance or augmentation of trees ≥84 cm dbh to increase the number of potential dens and to enhance the quality of den microhabitat in the lower Mississippi Alluvial Valley.

USE OF BODY MEASUREMENTS AND SERUM METABOLITES TO ESTIMATE THE NUTRITIONAL STATUS OF MALLARDS WINTERING IN THE MISSISSIPPI ALLUVIAL VALLEY, USA

We collected mallards (Anas platyrhynchos) from bottomland hardwood habitats on the Bayou Meto Wildlife Management Area and the White River National Wildlife Refuge, Arkansas County, Arkansas during the winter of 1990 to 1991 to determine if measures of physiological condition could be predicted from structural size, serum metabolite levels, or from direct measures of carcass composition. Serum triglyceride levels were correlated (r = 0.57, P = 0.007) with total body fat in males and slightly increased the value (from R2 = 0.64 to 0.76) of intact body mass alone for predicting total body fat in males. Overall, however, serum metabolites appeared to be poor indicators of the magnitude of nutrient masses in mallards. Three potential indices of nutritional status were developed from carcass composition data: protein/total ash, fat/ total ash, and fat/fat-free body mass. Protein masses of male mallards changed over winter (P = 0.02). Consequently, fat-free masses are not constant and represent poor indicators of structural size for mallards wintering in the Mississippi Alluvial Valley.

Serum enzymes as indicators of capture myopathy in mallards (Anas platyrhynchos).

Serum concentrations of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST) were measured in captive and wild mallards (Anas platyrhynchos) as indicators of muscle damage. Baseline values for both enzymes were determined from six captive male mallards. During winter 1990 to 1991, six diets (including controls) representative of food available in the Mississippi alluvial valley were fed to captive female mallards housed in an outdoor aviary at the White River National Wildlife Refuge, Arkansas County, Arkansas (USA). Controlled handling of penned mallards resulted in elevated serum CK (means = 1,352 IU/liter; SD = 1,212) and AST (means = 101 IU/liter; SD = 95) concentrations consistent with myopathies. These serum enzyme elevations were not affected (P > 0.3) by dietary selenium concentrations in the six diets or by energy malnutrition suffered by birds fed soybeans. Capture of wild mallards with an entanglement type rocket net resulted in serum CK and AST concentrations (means = 12,035 and 330 IU/liter; SD = 8,125 and 171, respectively) that were higher (P < 0.001) than those reported after capture with an enveloping type rocket net. Baseline values, controlled handling values, and entanglement rocket net values for serum CK and AST all differed (P < 0.0001).

A Field Test for Differences in Condition among Trapped and Shot Mallards

We tested predictions from the condition bias hypothesis (Weatherhead and Greenwood 1981) regarding the effects of sampling methods on body weights of mallards (Anas platyrhynchos) at White River National Wildlife Refuge (WRNWR), Arkansas, during 24 November-8 December 1985. Body weights of 84 mallards caught with unbaited rocket nets in a natural wetland were used as experimental controls and compared to the body weights of 70 mallards captured with baited rocket nets, 86 mallards captured with baited swim-in traps, and 130 mallards killed by hunters. We found no differences (P > 0.27) in body weight among sampling methods, but'body condition (wt/wing length) of the birds killed by hunters was less (P 0.75 for differences >50 g. The condition bias hypothesis probably applies to ducks killed by hunters but not to trapping operations when substantial (>20 at 1 time) numbers of birds are captured. J. WILDL. MANAGE. 52(2):227-232 Waterfowl researchers recognize the need to obtain representative samples when estimating survival, recruitment, and other population parameters (Brownie et al. 1985:6, Cowardin et al. 1985:29). Unfortunately, random sampling of waterfowl populations is impractical and detecting nonrepresentative samples requires knowledge of population parameters (Burnham and Nichols 1985). An alternative is to look for interpretable patterns of variation among sampling methods (Greenwood et al. 1986). Weatherhead and Greenwood (1981) recently reported that red-winged blackbirds (Agelaius phoeniceus) caught with mist nets differed in body weight and social structure from those captured in decoy traps. They interpreted the data as evidence that the blackbirds captured in decoy traps were in poor condition and not representative of the population. Considerable discussion regarding the implications of nonrandom sampling for waterfowl banding programs and population management ensued (Weatherhead and Ankney 1984, 1985; Burnham and Nichols 1985), but few new data were generated (Burnham and Nichols 1985, Greenwood et al. 1986). Our objectives were to design and conduct an experiment that would sample a population of mallards in Arkansas during early winter using 1 recovery and 3 capture methods, and test predictions from the condition bias hypothesis (Weatherhead and Greenwood 1981) regarding differences in body weight, condition, and social structure of mallards in relation to sampling methods. We are grateful to D. E. Delnicki, W. R. Noble, and A. M. Strong for help in trapping and examining mallards, and to J. E. Fraize for access to birds taken by hunters. C. M. Bunck and B. K. Williams assisted with data analysis and experimental design, and R. M. Erwin, G. M. Haramis, R. M. Kaminski, J. R. Longcore, and J. D. Nichols provided helpful comments on various drafts of the manuscript. CONCEPTUAL FRAMEWORK Heterogeneity of physical condition within populations can result in 2 types of bias. Statistical bias occurs when representative but heterogeneous samples cause estimators to be biased. This problem was addressed by Nichols et al. (1982). Sampling bias occurs when the initial capture or subsequent recovery processes (or both) are not representative with respect to a particular variable (e.g., condition), and that variable is correlated with a parameter of interest (e.g., survival). Our study was concerned with capture and recovery sampling biases. Weatherhead and Greenwood (1981) suggested that the biological basis for the differential condition between blackbirds captured in mist nets and decoy traps was the birds' foraging behavior. Blackbirds often feed by local enhancement wherein birds seeking food join oth-

A MAJOR OIL BARGE POLLUTION INCIDENT ON THE ARKANSAS RIVER

ABSTRACT When the towboat Girard Lewis lost power on the Arkansas River Navigation System, it drifted into a railroad bridge near Pine Bluff, Arkansas. Upon impact, it lost the two oil barges it was pushing; one barge floated downstream and was impaled by icebreakers on U.S. Army Corps of Engineers Lock and Dam No. 4. The resulting damage to the barge caused a major discharge (8,000 barrels) of No. 6 fuel oil, which affected industrial and recreational uses of the river and threatened sensitive environmental areas, including the White River National Wildlife Refuge. The discharger accepted responsibility for salvage of the damaged barge but not for containment and cleanup of the spilled oil. Consequently, the U.S. Environmental Protection Agency initiated a federal removal project using the oil pollution response fund authorized under the Clean Water Act. A coordinated effort among at least seven federal and state agency representatives on site was carried out over 25 days. Special problems were encountered and resolved involving unusually high river flow, large amounts of debris, use and effectiveness of various oil recovery devices, barge salvage operations, closure of the navigation system to traffic, protection of environmentally sensitive areas, and levels of cleanup of shorelines and locks and dams. The project was effectively carried out over 60 miles of affected river at a cost of $372,000, with a minimum of environmental and real property damages. It was the worst pollution incident that has occurred on the Arkansas River Navigation System.

Simulation of wetlands forest vegetation dynamics

A computer program, SWAMP, was designed to simulate the effects of flood frequency and depth to water table on southern wetlands forest vegetation dynamics. By incorporating these hydrologic characteristics into the model, forest vegetation and vegetation dynamics can be simulated. The model, based on data from the White River National Wildlife Refuge near De Witt, Arkansas, “grows” individual trees on a 20 x 20-m plot taking into account effects on the tree growth of flooding, depth to water table, shade tolerance, overtopping and crowding, and probability of death and reproduction. A potential application of the model is illustrated with simulations of tree fruit production following flood-control implementation and lumbering.