5.0 Macro-and Meso-Mammals of Futch and Howe Creeks

5.1 Introduction

Most macro-mammals (body mass >25 kg) and meso-mammals (body mass 2.5-25 kg) have been placed under severe stress from human-related causes as the southeastern United States has become more densely developed. Loss of habitat, over-hunting, and the introduction of exotic species has resulted in the extinction or extirpation of most of the southeast's macro-mammals (red wolf, gray wolf, West Indian monk seal, wapiti, buffalo), while the population numbers of others (panther, black bear) have become severely depleted. Community composition shifts dramatically as habitat is altered and native macro-mammals are removed, favoring an increase in the numbers of native meso-mammals (bobcat, gray fox, raccoon, opossum) and in the numbers of feral populations of introduced macro- to meso-sized mammals (domestic dog, cat, and livestock). Native macro-mammals typically are top-level carnivores and thus keystone species, so their extirpation also favors the range expansion of non-indigenous native macro- and meso-mammals (coyote and red fox). Each of these species, however, occupies a distinct niche and none are true ecological equivalents, so the change in community composition is not always one for one in terms of number of species or in terms of population size. Thus, population densities for most macro- and meso-mammals are tremendously altered from what they were before the southeastern United States was colonized by Europeans.

Another response to human induced environmental changes in the southeastern United States is the substantial increase in the numbers of three species of indigenous macro- and meso-mammals (white-tailed deer, beaver, river otter). Unregulated hunting and trapping caused precipitous declines in the population sizes of these species immediately after the United States was colonized, but since then numbers of each have rebounded and are, in some places, at all-time highs. Each species clearly has benefited from the extirpation of its natural predators, sound wildlife management practices, including restocking and habitat restoration programs, and their adaptability.

As populations of macro- and meso-mammals have changed in size and density, so has the amount of feces that they contribute to total community fecal biomass production. Although extirpated species no longer contribute to total community fecal biomass, the percentage of fecal biomass produced by other species of native macro- and meso-mammals has increased as their numbers have increased. In addition, the percentage of fecal biomass produced by exotic species (domestic dogs and cats, and especially domestic livestock) has increased as development has increased, bringing more of these animals into the region.

     This research was deemed necessary because it appears that the relatively high level of fecal coliform bacteria in some coastal creeks and estuarine communities may not be entirely anthropogenic in origin. The purpose of this study, therefore, was to test the hypothesis that the amount of feces produced by macro- and meso-mammals does not differ among clearly defined sections of Futch and Howe creeks in southeastern North Carolina, based on estimates of the relative abundances of each creek's macro- and meso-mammals.

5.2 Materials and Methods

I estimated the abundances of the macro- and meso-mammals that inhabited the Futch and Howe Creek watersheds using standard scat and track analyses. Each type of mammal sign was recorded by two or three people during surveys conducted on foot or by boat; most mammal sign, however, was discovered on foot. For comparative purposes, the watersheds of each creek were divided into five sections of about equal area. The Futch Creek watershed included the upper north arm, lower north arm, upper south arm, lower south arm, and lower creek, while the Howe Creek watershed included the north arm, south arm, upper creek, middle creek, and lower creek, with the Graham Pond area designated as the upper creek.  Mammals and their sign were recorded on six days, totaling approximately 72 man-hours in the Futch Creek watershed, whereas in the Howe Creek watershed a total of 67 man-hours was spent over the course of six days.

Indices of relative abundance were determined for each species in each section of each creek based on the type and number of spoor found in each, using the scale: absent, rare, uncommon, common, and abundant. One species of macro-herbivore (white-tailed deer), four species of meso-carnivores (red fox, bobcat, river otter, mink), three species of meso-omnivores (gray fox, raccoon, Virginia opossum), and two species of meso-herbivores (eastern gray squirrel, rabbit) and have been reported from similar habitats in southeastern North Carolina, whereas one macro-herbivore (domestic livestock), one macro/meso-omnivore (domestic dog), and one meso-carnivore (domestic cat) have been introduced into the region. To avoid biasing the results of this investigation, these analyses were conducted blind; that is, despite continued water monitoring by CMSR personnel over the last several years, I did not know the recent history of the fecal coliform concentrations in either creek. This paradigm predicted that sections of each creek with greatest relative abundance of meso- and macro-mammals should have the greatest fecal coliform levels.

5.3 Results  

Futch Creek

          Twelve species of macro- and meso-mammals were found to inhabit the Futch Creek watershed (Table 5.1), including nine native and three exotic species. Evidence of the bobcat was not found during the course of this investigation.  The nine native species included one macro-herbivore (white-tailed deer), three meso-carnivores (red fox, river otter, mink), three meso-omnivores (gray fox, raccoon, Virginia opossum), and two meso-herbivores (eastern gray squirrel, rabbit). Evidence of the otter, mink, red and gray foxes, and rabbit was so rarely encountered that it was difficult to determine their impacts on the watershed. Deer, judged to be relatively uncommon from the number of tracks and scat seen, were most numerous around the upper north arm where there was scant development. Raccoons were common to abundant in the Futch Creek watershed; they were seen sleeping in oak trees, skeletal material was recovered, and hundreds of scats and tracks were counted. Athough they were common in the upper reaches of both arms, raccoons were more abundant along the lower reaches of both arms and the lower creek. Opossums were uncommon and more or less evenly spaced around the perimeter of Futch Creek. Based on the number of nests, feeding stations, and individuals sighted, squirrels were uncommon to abundant around Futch Creek, depending on which part of the creek was being considered. They were relatively uncommon along the upper reaches of both the north and south arms where riparian vegetation was densest, common along the lower reaches of the north arm and both sides of the lower creek, and abundant along the lower reaches of the south arm where the understory has been removed but houses and outbuildings have not yet been built. Densities have apparently diminished after buildings were constructed and domestic cats arrived.

The three Futch Creek exotics included one macro-herbivore (domestic livestock), one macro/meso-omnivore (domestic dog), and one meso-carnivore (domestic cat), which were relatively uncommon around Futch Creek. Dogs and cats appeared to be evenly spaced around the lower reaches of both arms and the lower creek's perimeter based on the few scats, sets of tracks, and individuals observed, but largely absent from the upper reaches of each arm. Conversely, evidence of livestock was most commonly found in the headwaters of Futch Creek, especially adjacent to the upper south arm.

Howe Creek

         Eleven species of macro- and meso-mammals were found to inhabit the Howe Creek watershed (Table 5.2), including eight native and three exotic species. Evidence of the bobcat and mink was not found during the course of this investigation.  The eight native species included one macro-herbivore (white-tailed deer), two meso-carnivores (red fox, river otter), three meso-omnivores (gray fox, raccoon, Virginia opossum), and two meso-herbivores (eastern gray squirrel, rabbit). Evidence of the otter, red and gray foxes, opossum, and rabbit was so rarely encountered that it was not possible to assess their impacts on the watershed. Deer were uncommon to abundant around Howe Creek, and their densities varied tremendously. Based on the number of tracks, scat, skeletal remains, and other spoor (but not electric fencing!), densities were greatest on the south side of the upper, middle, and lower sections of the creek. Deer were uncommon around the south arm of Howe Creek and between the north and south arms, but rare to uncommon along the north side of the north arm and upper, middle, and lower sections of Howe Creek.  Raccoons, which were frequently seen sleeping in the tops of large oaks, were common to abundant and more or less evenly distributed around the perimeter of Howe Creek. They were abundant along both sides of the upper, middle, and lower sections of the creek and common around both arms. Squirrels were uncommon to common around Howe Creek. They were relatively uncommon along both the north and south arms, which are densely vegetated, but common along both sides of the upper, middle, and lower creek.

The three Howe Creek exotics included one macro-herbivore (domestic livestock), one macro/meso-omnivore (domestic dog), and one meso-carnivore (domestic cat). Each was relatively uncommon around Howe Creek. Dogs and cats appeared to be evenly spaced around the lower reaches of both arms and the upper, middle, and lower sections of the creek's perimeter based on the few scats and sets of tracks observed, but they were largely absent from the watershed adjacent to each arm. Livestock were largely absent from the Howe Creek watershed.

5.4 Discussion

Whether species are considered individually or together, the densities of macro- and meso-mammals were not consistent around the perimeter of Futch Creek. The south arm, which is largely wooded or cleared for agriculture in its headwaters but moderately developed above its merger with the north arm, had greater richness in the number macro- and meso-mammals, and it had greater population densities when all species are considered together. The lower creek, which was more densely developed, had slightly less richness and total density. The north arm, which is heavily wooded and sparsely developed, had the lowest total density. Along the length of the south arm and lower creek, there was a gradual replacement of native macro- and meso-mammals with introduced species. The north arm, on the other hand, exhibited little change in species composition along its length. This change is imminent, however, as the north arm is currently being developed.

Densities of macro- and meso-mammals were also not consistent around the perimeter of Howe Creek. Total mammal density was greatest in the lower and middle sections of the creek, and it gradually decreased as one moved up the watershed. The headwaters of Howe Creek were impacted by development long before the mouth of the creek was developed, apparently forcing mammals towards the intracoastal waterway. The mouth of the watershed, which currently is acting as a refugium for macro- and meso-mammals that no longer inhabit the headwaters of the creek, had large numbers of deer on the south bank where the last remaining segment of relatively large undisturbed habitat once stood. The shift in species composition, from native to introduced species, was more apparent on the north shore, where development began earlier and is more dense, as compared to the south shore.

          If the relative densities of native and introduced macro- and meso-mammals are related to the amount of fecal coliform in coastal creeks, then the south arm of Futch Creek and the waters downdrift of the south arm should have the highest levels of fecal coliform (this is indeed the case in Futch Creek - see Chapter 4). Likewise, fecal coliform levels in Howe Creek should gradually increase along its length towards its mouth (this is not the case, however, due to higher salinities and flushing near the creek mouth - Chapter 4). Other predictions of this paradigm are that fecal coliform in the north arm of Futch creek will increase as that region is developed, further increasing coliform levels in the lower creek, and that fecal coliform levels in Howe Creek will increase as native macro ­and meso-mammals are extirpated from the region.