Human-altered Habitats Research Articles

Use of Altered Habitats by the Endemic Sand Skink (Plestiodon reynoldsi Stejneger)

Endemic species with limited geographic ranges are particularly sensitive to habitat loss and degradation. In order to conserve such species, we tend to focus on optimal habitats (e.g., for land acquisition), but human-altered habitats may also be of conservation value if species can persist in these environments. We evaluated the occurrence of a lizard endemic to scrub and sandhill habitats in Florida, the threatened Plestiodon reynoldsi (Sand Skink), to determine whether it occurs in human-altered vegetation types. From 2003–2004, we quantitatively sampled 46.5 ha (composed of 7 vegetation and 10 soil types) for the distinctive trails this fossorial lizard leaves in sandy areas. The Sand Skink was present in equal relative densities across all vegetation types, including disturbed areas such as pastures and abandoned citrus groves. Further, we detected Sand Skinks on all well-drained sandy soils we sampled. Thus, Sand Skinks can persist in human-altered habitats, at least when underlying soils are suitable for their presence and have not been modified. In general, more Sand Skinks were found in larger habitat patches, regardless of whether patches were characterized by vegetation or soil. Our results suggest that anthropogenically altered habitats have conservation value for Sand Skinks (and possibly other ecologically similar species) and that future studies should focus on the effects of restoring these habitats on resident populations of this species.

Effects of human disturbance on movement, foraging and bed selection in red deerCervus elaphus xanthopygus from the Wandashan Mountains, northeastern China

We characterized 716 sites (including 22 beds, 60 foraging and 604 movement sites) used by red deerCervus elaphus xanthopygus Milne-Edwards, 1867 in the Wandashan Mountains, northeastern China in the winter period. We used covariates for vegetation, topography, disturbances by other ungulates, and disturbance by humans to develop movement, forage and bed site resource-selection models. We used an information-theoretic approach to select the top 5 models for movement, forage and bed site occurrences respectively. The three most parsimonious autologistic models were good predictors of movement, forage and bed occurrence of this species. Vegetation covariates were important components of all models. We recorded avoidance responses by the behaviours of species to each disturbance type (ie, villages, forest roads and abandoned roads); bed site occurrences were most sensitive to all human disturbances for their lowest odds encountered. Across all parsimonious models, villages have the largest negative effect on movement, foraging and bed occurrences. Movement and bedding behaviours were also affected by other ungulate disturbances. Altitude had slightly negative effect on movement and foraging behaviours. Ridges, topographic aspect and shrub stands were all correlated with bed-site selection. Although different behaviours may be associated with different microhabitat features, behaviours of red deer responded similarly to the same human disturbance on a broad scale. Based on the observations above, we believe that red deer are avoiding human-altered habitat for movement, bedding and foraging because of disturbances during the critical late winter period. Furthermore, various behavioural resource selection models and corresponding graphs of important habitat disturbances can be used to guide and evaluate future development proposals.

Associations of anthropogenic activity and disturbance with fitness metrics of eastern bluebirds ( Sialia sialis)

To predict the long-term consequences of increasing human activity and environmental disturbance on natural populations, it is imperative to understand how human activity relates to fitness variation in wild populations. Here, we report associations of avian fitness metrics with multivariate indices of human activity and bird behavioral responses in eastern bluebirds ( Sialia sialis). We quantified patterns of human activity, adult bird behavioral time budgets, and four avian fitness metrics (brood growth, brood condition, brood survivorship and nest box productivity) at 52 nest boxes placed along a human disturbance gradient. We found that distance of human activity relates nonlinearly to chick survival and productivity. Nests were more productive at intermediate levels of human activity. The number of box-visits completed by parent bluebirds was positively related to box productivity. We also found a significant negative relationship of intense and variable human activity with adult bird self-maintenance behaviors. These results suggest that adult bluebirds generally buffer their developing broods from human activity in the environment, sacrificing self-maintenance behaviors before compromising the growth and survival of their brood. If adult birds are absorbing the costs of anthropogenic disturbance in lieu of their young, there could be negative sub-lethal consequences of increasing human activity for future breeding attempts. The nonlinear relationships we found between human activity and avian fitness indicate that eastern bluebirds are somewhat pre-adapted to intermediate levels of human disturbance. As local populations have gone through a recent population bottleneck and experienced intense selection for breeding in man-made cavities in the past 40–50 years, we speculate that local populations may have adapted rapidly to human altered habitats. Hence, we advocate a more inclusive evolutionary ecology approach to understanding responses of natural populations to human disturbance.

SIMILARITIES IN CALLING SITE AND ADVERTISEMENT CALL AMONG ANURAN AMPHIBIANS IN SOUTHEASTERN BRAZIL1

We hypothesized that species that overlap in calling sites partition the acoustic space, whereas those that segregate calling sites overlap in the acoustic space. Most of the 12 analyzed species (75%; n = 9 species) were generalists with respect to at least one of the calling site variables, a characteristic of species living in unpredictable or human-altered habitats. In most water bodies, segregation in calling sites occurred as a result of low species richness in the communities. Higher overlaps in calling sites were observed among species that called from the ground or while floating in water than among those that called perched on vegetation, probably due to differences in the use of two- versus three-dimensional spaces. As a result of the analysis of similarity among advertisement call features, we observed higher segregation among species that called on the ground or floating on water than perched on vegetation. For those species, differences in advertisement calls seem to explain their coexistence.

Distribution of ground-dwelling beetles in fragmented tropical habitats

The conservation of biodiversity is increasingly dependent on human-altered habitats. In a fragmented forest landscape in northern Costa Rica within the Mesoamerican Biological Corridor, an area of great conservation importance, we compared the diversity and composition of ground-dwelling beetle communities in five habitat types along a gradient of increasing disturbance: primary forest, logged forest, secondary forest, plantation (Gmelina arborea) and pasture. Using pitfall trapping we captured a total of 1,877 beetles (Coleoptera), comprising 422 morphospecies in 26 families. The plantation sites had the lowest number of species followed by secondary forest and pasture. Multivariate analysis separated the beetle fauna according to land use, and suggested that only the logged forest maintains a similar species assemblage to primary forest. However, each habitat harboured a number of unique species indicating the conservation value of the mosaic of habitats found in fragmented landscapes. Our results suggest that to maintain forest beetle species diversity it is essential that areas of natural forest are conserved. However, other land uses also provide beetle habitats and in fragmented areas active management to maintain a mosaic of land uses will contribute to the conservation of beetle diversity.

DIETS OF SWIFT FOXES (VULPES VELOX) IN CONTINUOUS AND FRAGMENTED PRAIRIE IN NORTHWESTERN TEXAS

Distribution of the swift fox (Vulpes velox) has declined dramatically since the 1800s, and suggested causes of this decline are habitat fragmentation and transformation due to agricultural expansion. However, impacts of fragmentation and human-altered habitats on swift foxes still are not well understood. To better understand what effects these factors have on diets of swift foxes, scats were collected in northwestern Texas at two study sites, one of continuous native prairie and one representing fragmented native prairie interspersed with agricultural and fields in the Conservation Reserve Program. Leporids, a potential food source, were surveyed seasonally on both sites. Diets of swift foxes differed between sites; insects were consumed more on continuous prairie, whereas mammals, birds, and crops were consumed more on fragmented prairie. Size of populations of leporids were 2-3 times higher on fragmented prairie, and swift foxes responded by consuming more leporids on fragmented (11.1% frequency occurrence) than continuous (3.8%) prairie. Dietary diversity was greater on fragmented prairie during both years of the study. Differences in diets between sites suggested that the swift fox is an adaptable and opportunistic feeder, able to exploit a variety of food resources, probably in relation to availability of food. We suggest that compared to continuous native prairie, fragmented prairie can offer swift foxes a more diverse prey base, at least within the mosaic of native prairie, agricultural, and fields that are in the Conservation Reserve Program.

Predictors of biting fly harassment and its impact on habitat use by feral horses (Equus caballus) on a barrier island

Feral horses on Assateague Island, Maryland, were observed in June and August 2000 to determine what behavioral and ecological factors affect the intensity of biting fly harassment and whether habitat use by horses was influenced by biting flies. Fly counts and frequencies of comfort movements (i.e., movements designed to dislodge insects) were recorded during focal animal samples, as well as data on sex, group size, habitat type, temperature, humidity, wind speed, and behavior. Seasonal habitat use patterns were assessed using 7 years of monthly census data on the horses. The number of biting flies on the horse was affected by horse sex, habitat, temperature, and group size. The number of comfort movements a horse showed was affected by habitat, temperature, wind speed, group size, and number of horses within one body length of the focal. The number of comfort movements made by a horse was found to be highly correlated with fly numbers. Though marshes were used most throughout the year, the pattern of use of dune, scrub, and human-altered habitats reflects a pattern of biting fly avoidance and refuge-seeking by the horses.

Habitat use of adult White-throated Robins during the breeding season in a mosaic landscape in Costa Rica

Abstract Most work on the effects of land-cover change on tropical birds has focused on forest-interior birds because these species are assumed to be the most severely affected by forest loss. However, even species that use human-altered habitat types may be severely affected by forest loss. White-throated Robins (Turdus assimilis) frequently nest in coffee and pasture in southern Costa Rica, although several lines of evidence suggest the species could not exist solely in agricultural habitat. We used radio-telemetry to examine the area and proportion of different habitat types used by adult White-throated Robins. Mean area of use for the tracking period was 0.26 km2 and varied from 0.07 to 0.58 km2. No robins had areas of use solely in either primary forest or agricultural cover, although individuals were initially captured in both primary forest and a coffee plantation. All areas of use contained some forest, pasture, and coffee or regenerating forest. The mean percentages of the habitat types used by t...

Successful lizard eggs in a human-disturbed habitat.

As humans extend their influence to an increasingly large portion of the globe, it becomes of both theoretical and practical interest to understand the consequences of our activities on wildlife populations. Norops polylepis is a small anoline lizard native to rainforest of southern Costa Rica. It is also found and known to lay eggs in cattle pastures immediately adjacent to forest. I predicted that N. polylepis eggs would fare poorly in pastures because of the important abiotic and biotic differences with their native forest habitat. I obtained eggs from captive females and estimated an egg's probability of hatching, daily survival rate, and incubation time at various distances along a forest-to-pasture gradient. Contrary to expectation, egg survival rates were higher in pastures than in forest areas. Furthermore, egg incubation times were significantly shorter in pastures than in their native forest. As a result, eggs were at least as likely to hatch in pastures as in forested areas. Thus, pastures may represent a benign or even beneficial habitat for the eggs of some reptile species. High survival of eggs will facilitate range expansion into human-altered habitats such as pastures, but does not guarantee it. Indeed, pastures could represent an ecological trap and a population sink if adults are drawn there (e.g., in search of favorable ovipositioning sites) yet suffer higher mortality than in forests.

The western screech-owl and habitat alteration in Baja California: a gradient from urban and rural landscapes to natural habitat

We studied the western screech-owl (Otus kennicottii) in the desert of the southern Baja California peninsula to determine its status and habitat selection and whether it benefits from moderate human-caused habitat changes. Based on the response to tape-recorded call broadcasts, western screech-owls were more abundant in undisturbed vegetation than in human-altered habitat. In man-made environments, more owls responded in rural than in urban areas; indeed, they were practically absent in urban areas. In natural areas, a total of 1.6 owls/km was estimated in the nonbreeding season and 2.7 owls/km in the breeding season. The most important habitat features selected in natural areas were greater shrub cover in the strata containing shrubs 1–2 and 2–3 m high and greater canopy cover of trees >5 m high. In rural areas adjacent to cultivated areas, owls were present in areas with the greatest cover of shrubs 1–3 m high and a higher density of shrubs. The western screech-owl also occurs at lower densities in rural areas than in natural areas. Towns appear to be avoided in the arid desert of Baja California Sur. Western screech-owls may be still able to persist in rural areas that occupy an intermediate position on the gradient from a functional natural system (desert vegetation) to a completely altered ecological system, urbanized areas.

Reproductive traits in common toad Bufo bufo from the vicinity of Belgrade

Common toad Bujo bufo is a species with wide geografical and altitudinal distribution in Europe (A I' n old 2002). Although it prefers forests, mainly deciduous, it also occurs in fields, meadows, gardens and human settlements (R ado van 0 vic 1951). The aims of this study were to analyse the annual reproductive cycle of Bufo bufo, as a part of the study on reproductive traits in amphibian populations from human-altered habitats, with special emphasis on sites in the vicinity of Belgrade; to compare seasonal changes in relative organ weights in both sexes; to examine variation in fecundity and relationship between fecundity and body size.

Patterns of human disturbance and response by small mammals and birds in chaparral near urban development

We report on the extent of disturbance (including habitat alteration and road and trail proliferation) in chaparral near urban development and analyze the effects of disturbance on small mammal and resident bird species. Disturbance patterns were evaluated in a 6700 ha study area in southern California: effects on mammals and birds were investigated by analyzing relationships between vegetation structure and animal species richness and abundance. Disturbance was prevalent throughout the study area and included extensive human-altered habitat (from past human activities such as vegetation clearing, human-caused fires, refuse dumping, and vegetation trampling) and 157 km of roads and trails. A nonsignificant trend was found between human-altered habitat and proximity to development, but human-altered habitat was significantly associated with roadway proximity. Trails were also more frequent near urban development and roads. Small mammals responded strongly to disturbance-related vegetation changes, while birds showed little or no response. Mammals endemic to chaparral vegetation were less diverse and abundant in disturbed sites, whereas disturbance-associated species increased in abundance. Close proximity of urban development to natural areas resulted in alteration of natural habitat and proliferation of roads and trails. Variation in life history traits between birds and mammals may affect response to disturbance and influence persistence if disturbance continues. Conservation efforts must recognize the potential for habitat damage and associated declines in native animal species caused by disturbance near urbanization and implement strategies to reduce these threats.

Anthropogenic Effects on Winter Behavior of Ferruginous Hawks

Little information is known about the ecology of ferruginous hawks (Buteo regalis) in winter versus the breeding season and less about how the species adapts to fragmented grassland habitats. Accordingly, we studied the behavior of 38 radiotagged ferruginous hawks during 3 winters from 1992 to 1995. We used 2 adjacent sites in Colorado that were characterized by low and high levels of anthropogenic influence and habitat fragmentation: the Rocky Mountain Arsenal National Wildlife Refuge (RMANWR; low-level influence), and several adjacent Denver suburbs (high-level influence). Relative abundance of ferruginous hawks differed by treatment area and year (P 0.05) at RMANWR and suburban sites. Ferruginous hawks appear to modify their behavior in fragmented, largely human-altered habitats, provided some foraging habitats with adequate populations of suitable prey species are present.

Technical and environmental factors involved in birds electrocution on power lines

Technical and environmental factors responsible of bird electrocution have been analyzed in low and medium tension power lines in a bird important area placed in the south of Alicante province (SE Spain). One hundred eighty six dead birds (119 birds of prey) have been located in 182 poles inspected. Most species are legally protected and some are in jeopardy. Some pole types with suspended insulators have caused the same number of victims than poles with rigid insulators. Poles with rigid insulators in two levels produce more accidents than poles with one level. A different pole use according to the habitat has been observed. Birds of prey avoid poles in cultures, in the vicinity of roads and in flatlands or in hill tops. Furthermore, more electrocutions occur near bath zones. Poles in high places and located near to human altered habitats, where feeding is easy, are preferred by remainder birds.

Habitat Use by White-Tailed Deer on Cross Timbers Rangeland following Brush Management

Seasonal habitat use by white-tailed deer (Odocoileus virginianus Zimmerman) was monitored with radio telemetry in 1988-89 to determine responses to experimental brush treatments, 5-6 years post-treatment, in the cross timbers region of central Oklahoma. The study area was a mosaic of brush treatments: tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiazol-2-yl 1]-N,N'-dimethylurea) herbicide, tebuthiuron with an annual spring burn, triclopyr ([(3,5,6-trichlor-2-pyridinyl)oxy]acetic acid) herbicide, triclopyr with an annual spring burn, and no herbicide with annual spring burning. Control areas with no burning or herbicide applications also were evaluated. Herbicides were applied in 1983, and fires were initiated in 1985. Annual home range (95% harmonic mean) averaged 99.9 ha, and no differences in size among seasons or between sexes were observed. Both sexes selected and avoided specific brush treatments throughout the year. Female deer selected or avoided more human-altered habitats in specific contrasts of main treatment groups (e.g., treated vs. control, herbicide vs. no herbicide, fire vs. no fire, etc.) than males. Both sexes selected fire treatments in summer and were most particular in their choice of main treatment groups in summer and fall habitat use between the sexes was most similar in winter and most disparate in fall. The mosaic of habitat types resulting from the variable herbicide and burn application pattern probably influenced deer habitat use in the cross timbers region through combined effects of increased mid-story cover and forage production as they relate to reproductive activities and nutritional needs of female deer in particular.

Effects of rain forest disturbance and fragmentation: comparative changes of the raptor community along natural and human‐made gradients in French Guiana

A density index of every diurnal raptor species (Falconiformes) was obtained on 101 400 ha sample plots distributed among eight natural habitats and five man‐made habitats arranged along gradients of increasing forest degradation and fragmentation. The most significant structural parameter affecting species distribution was the tall canopy forest cover. Species richness, diversity and density all decreased with this mature forest cover index. Individual species and overall community densities decreased along the deforestation gradient but the species richness was partly maintained by species turnover. Six groups of species were identified according to their natural habitat preferences. Their distribution along the deforestation gradient was correlated with their natural habitat selection pattern. Thus the community composition of each vegetation or landscape type was predictable. Fifty‐six percent of the regional assemblage of species had their optimal density in the primary forest. A third of them were interior forest species highly sensitive to forest disturbance and opening. The other two‐thirds were upper canopy, gap or edge species more tolerant to forest fragmentation. The last twenty‐one species were associated with various coastal habitats, from dense forest patches to mangrove and savanna. Again, one third of them were strictly restricted to their specialized habitats while the last two‐thirds colonized human‐altered habitats and progressively replaced primary forest species with increasing deforestation. The maintenance of large areas of every natural habitat was essential for the conservation of (1) the whole population of a third of the total raptor diversity and (2) optimal and presumably potential source populations of most other species surviving in human‐modified habitats.