Road Counts Research Articles

Vegetation structure and ungulate abundance over a period of increasing elephant abundance in Hwange National Park, Zimbabwe

This study investigates whether increases in elephant populations may influence the structure of African savannas, and consequently may affect other herbivores through changes in habitats. Two contrasting periods in terms of elephant population densities were compared in Hwange National Park, Zimbabwe: the early 1980s and the late 1990s. Elephant population density and other ungulate population densities were estimated for a c. 400-km2 area from road counts. Vegetation structure at the landscape scale was assessed using aerial photographs for the same area. All browsers and grazers declined between the early 1980s and the late 1990s, whereas elephants experienced a 16-fold increase. At the landscape scale, vegetation structure changed little with no evidence of an opening of the habitats. These results do not support any kind of medium-term facilitation between elephants and other herbivores. They rather suggest a negative effect of elephants on other herbivore species when elephants are present at high densities. This study rules out a scenario where the decrease of the different herbivore populations was caused by large changes in vegetation structure due to elephant activity.

Counting a suburban deer population using Forward-Looking Infrared radar and road counts

Abstract Population estimates of white-tailed deer (Odocoileus virginianus) are critical to advancing the process of community-based deer management. One of the first questions raised by residents of suburban areas is “How many deer live in our community?” Our objective was to evaluate the reliability and cost of helicopter-mounted Forward-Looking Infrared (FLIR) in detecting and counting a suburban white-tailed deer population as compared to road counts. We conducted 4 separate road counts 1 hour prior to sunset between June 2001–January 2002. The average number of deer counted based on road counts was 229 (SE = 10.04). We conducted 3 separate flights using a helicopter-mounted FLIR between 2000–2330 hours on 9 January 2002. The average number of deer counted using FLIR was 214 (SE = 18.7). Both population survey methods yielded similar results (P = 0.46). We recommend using FLIR in suburban areas dominated by private property where ground access or site distances may be limited, or where conducting a ro...

POPULATION DENSITY OF THE ENDANGERED FLORIDA KEY DEER

Abstract With decreased illegal hunting and better habitat conservation, the Florida Key deer (Odocoileus virginianus clavium) population grew from an estimated 25–50 animals in the late 1940s to approximately 200 animals on Big Pine and No Name keys, Florida, USA, by 1971, the last official survey. U.S. Fish and Wildlife Service (USFWS) trend data indicate that the deer population continued to increase after 1971; however, current deer density estimates are necessary for the proposed reclassification of the Key deer from endangered to threatened. Our study objectives were to (1) obtain current population estimates of Florida Key deer and compare these to historical estimates, (2) evaluate survey methods (USFWS mortality and deer counts) in detecting changes in population trends, and (3) outline a protocol for future monitoring. Road counts (n = 889) were conducted from January 1971 to December 1971 and January 1976 to December 2001 on Big Pine and No Name keys. From mark–recapture data, we estimated that...

Growth of the sika deer (Cervus nippon yakushimae) population in the western lowland forests of Yakushima Island, Japan

The density of a sika deer population in an evergreen natural forest on Yakushima Island was surveyed by road counts from August 1988 to July 1989, and from August 2001 to July 2002. Based on distance-sampling methods, population density estimates were 2.55 deer/km2 in 1988 and 40.74 deer/km2 in 2001. Encounter rate indices (number of deer seen per kilometer) increased by a factor of 6.16 over these 13 years. This rapid population growth may reflect increased sika deer food availability following logging in the forest.

Prey selection of lions <i>Panthera leo</i> in a small, enclosed reserve

Annual trends in numbers of ungulate species on a 15 km² reserve from 1993 to 1998, were evaluated in the context of lion Panthera leo reintroduction during 1996, and subsequent predation by them. The ungulate prey base was enumerated annually by aerial counts and a road count that took place during 1998. The lion prey record was obtained from direct observations of a radio-located pride of eight lions and daily reserve management records. All ungulate species that underwent precipituous declines were also the most important prey to lions, comprising over 80 % of their prey, and they were preyed upon according to their availability. Lion predation was causal for the declines in wildebeest Connochaetes taurinus, Blesbok Damaliscus pygargus phillipsi and Warthog Phacochoerus africana, while the decline in Kudu Tragelaphus strepsiceros was only partly ascribed to lions, as other non-lion related mortality sources were identified. The only ungulate species to increase subsequent to lion reintroduction was the Impala Aepyceros melampus, which was furthermore under-selected by lions. The uncontrolled population growth of Impala could have elicited ecological degradation, and it was advised to either not stock Impala, or otherwise control their numbers if lions are unable to do so. Lion hunting success and kill rate, were 21 % (n = 63) and 1 kill/4.4 days, respectively. Three bushpigs Potamochoerus larvatus were killed but not utilised,and this finding is corroborated by an intensive study in Kwazulu-Natal, and this aversion is discussed. Predators can cause unprecedented declines of their prey where the prey are confined to small reserves that have no refuge from predation. On an annual basis, prey may need to be augmented to sustain predators on small reserves

Impact of livestock and settlement on the large mammalian wildlife of Bale Mountains National Park, southern Ethiopia

Large mammals, both wild and domestic, were censused in four study areas in Bale Mountains National Park (BMNP), southern Ethiopia, from April until August 1997, using established road counts, horse-back counts and systematic transects, a new approach to censusing large mammals in BMNP. Data collected since 1983 were also examined to indicate trends in mammalian abundance. Civil unrest following the government changeover in 1991 disrupted management of BMNP, leading to an increase in human settlement and livestock densities. The effect of these factors on BMNP's wildlife is assessed and discussed. Most large mammalian wildlife has declined since 1983 but signs of recovery for some species in recent years are positive. The fates of two charismatic endemics are emphasised. BMNP's current population of mountain nyala ( Tragelaphus buxtoni, an endangered antelope) was estimated to be between 1100 and 1300. This is lower than estimates for the late 1980s, but shows an increase from very low levels recorded following social turmoil during the government changeover in 1991. Data on the Ethiopian wolf ( Canis simensis, a critically endangered canid) also indicate positive trends in abundance, following severe declines between 1989 and 1992 due to rabies epizootics. Action to reduce human utilisation of parts of BMNP is urgently required to prevent further degradation of the environment and to safeguard the future of both the mountain nyala and Ethiopian wolf.

Population indices for wild carnivores: a critical study in sand-dune habitat, south-western Queensland

Populations of feral cats, foxes and dingoes were assessed at four sites in the northern Simpson Desert from May 1995 to October 1996 using track counts. Counts were based on presence/absence of footprints on sandplots placed randomly throughout each of the four sites, with all habitats being sampled in accordance with their availability. Sandplots were repositioned between sampling periods so that data were temporally independent. This unbiased method was used to assess the reliability of more conventional indices of carnivore abundance based on spotlighting and counts of footprints on roads, which were run concurrently with the random sandplot counts. The sandplot data were also used to assess habitat use of the three study species. Counts on regularly spaced sampling plots along roads were correlated with random sandplot counts for foxes, but not for cats. Conversely, an index of activity based on counting individual tracks along roads was correlated for cats, but not for foxes. Spotlighting counts appeared to have little relationship with random sandplot counts for either species, with random sandplot counts and spotlight counts of foxes being correlated for only one of the four sites and no correlations being apparent for cats. The sandplot data showed that cats used dune crests preferentially over other habitats, while foxes preferred both dune crests and roads. Dune crests are probably used as natural runways by both species. Dingoes used roads preferentially over other habitats. It was concluded that differences in the use of roads and other runways by the carnivores can potentially lead to biases in indices collected along roadways. In relation to the random sandplot counts, foxes were overestimated by road counts and spotlighting relative to cats, the latter bias being related possibly to temporal differences in the activity patterns of the two species.

Population indices for wild carnivores: a critical study in sand-dune habitat, south-western Queensland

Populations of feral cats, foxes and dingoes were assessed at four sites in the northern Simpson Desert from May 1995 to October 1996 using track counts. Counts were based on presence/absence of footprints on sandplots placed randomly throughout each of the four sites, with all habitats being sampled in accordance with their availability. Sandplots were repositioned between sampling periods so that data were temporally independent. This unbiased method was used to assess the reliability of more conventional indices of carnivore abundance based on spotlighting and counts of footprints on roads, which were run concurrently with the random sandplot counts. The sandplot data were also used to assess habitat use of the three study species. Counts on regularly spaced sampling plots along roads were correlated with random sandplot counts for foxes, but not for cats. Conversely, an index of activity based on counting individual tracks along roads was correlated for cats, but not for foxes. Spotlighting counts appeared to have little relationship with random sandplot counts for either species, with random sandplot counts and spotlight counts of foxes being correlated for only one of the four sites and no correlations being apparent for cats. The sandplot data showed that cats used dune crests preferentially over other habitats, while foxes preferred both dune crests and roads. Dune crests are probably used as natural runways by both species. Dingoes used roads preferentially over other habitats. It was concluded that differences in the use of roads and other runways by the carnivores can potentially lead to biases in indices collected along roadways. In relation to the random sandplot counts, foxes were overestimated by road counts and spotlighting relative to cats, the latter bias being related possibly to temporal differences in the activity patterns of the two species.

Measuring the contribution of randomness, exposure, weather, and daylight to the variation in road accident counts

Measuring the contribution of randomness, exposure, weather, and daylight to the variation in road accident counts

Elephant decline in Lake Manyara National Park, Tanzania

SummaryThe population of African elephant (Loxodonta africana (Blumenbach)) in Lake Manyara National Park, northern Tanzania, declined from about 500 individuals in 1984, to about 150 in 1988 due to poaching (mortality rate about 60% p.a.). In 1991 the population had declined further to about 60 individuals (mortality rate about 30% p.a.). In 1984 and 1991 road counts in the park were conducted. In 1984 a total distance of 2705 km was covered which yielded sightings of 777 elephant groups. In 1991 this distance was 5486 km and only 53 groups were observed. In both years an average elephant was seen in a group of seven individuals. Poaching pressure, apparently, had no effect on average group sizes. Group size changes with season, both in 1984 and 1991. The smallest groups were observed during the dry season when Acacia tortilis pods provided a defendable resource.In 1984, elephant occurred significantly more than expected in groups of five‐nine individuals and less than expected in groups of one or two individuals or in groups larger than 16. This has been interprétéd as a confirmation of the family structure of elephant as reported in other studies. In 1991, elephant group sizes were distributed according to a model of random association of individuals, indicative of destruction of the social framework by poaching.RésuméLa population d'éléphants africains {Loxodonta africana Blumenbach) au Pare National du lac Manyara, au nord de la Tanzanie, a baissé de près de 5000 individus en 1984 à près de 150 en 1988, à cause du braconnage (taux de mortalité de près de 60% p.a.). En 1991, la population avait encore baissé jusqu'à environ 60 individus (taux de mortalité de prés de 30% p.a.). En 1984 et 1991, on a fait des comptages dans le pare par la route. En 1984, on a parcouru une distance totale de 2705 km et repéré 777 groupes d'éléphants. En 1991, cette distance a été portée a 5486 km, et on n'a observé que 53 groups. Les deux années, le groupe moyen comptait sept individus. La pression du braconnage ne semblait pas avoir d'effet sur la taille des groupes, mais celle‐ci changeait avec les saisons, tant en 1984 qu'en 1991. On observait les plus petits groupes en saison sèche, lorsque les gousses d'Acacia tortilis représented une ressource à défendre.En 1984, on rencontrait significativement plus de groupes de cinq à neuf éléphants qu'on ne l'aurait prévu, et moins de groupes de un ou deux et de plus de seize. On a interprété ceci comme une confirmation de la structure familiale des groupes d'éléphants dont parlent d'autres recherches. En 1991, la taille des groupes d'éléphants se répartissait selon un modéle aléatoire d'association d'individus, indiquant une destruction par le braconnage de la structure sociale.

THE ABUNDANCE AND MOVEMENTS OF LUDWIG'S BUSTARD NEOTIS LUDWIGII

Summary Allan, D.G. 1994. The abundance and movements of Ludwig's Bustard Neotis ludwigii. Ostrich 65: 95–105. An analysis of bird-atlas data, road counts, an aerial census, and landowners' comments confirmed that Ludwig's Bustard Neotis ludwigii is a winter migrant to the winter-rainfall Succulent Karoo biome. In addition, the species appears to migrate seasonally between the Namib and Namibian Escarpment regions. There is no evidence, however, that the abundance of the species decreases in the summer-rainfall Nama Karoo biome during the winter. There was a Significant positive correlation between Ludwig's Bustard densities, as measured during road counts, and the total rainfall in the three months before each count, but this explained relatively little of the variation in Ludwig's Bustard densities. The total population size of the species was estimated at between 56 000 and 81000 individuals.

A new approach for detecting visibility bias for the fixed‐width transect method

SummaryFour road counts and four series of daily road counts of 28.4% sampling intensity were carried out at Wildlife Ranching and Research Ltd (WRR), Athi River, Kenya, between December 1966 and July 1987 to test the applicability of the method to the WRR environment. The results, however, exhibited high variation. Difficulties were encountered when applying the Anderson & Pospahala (1970) method to detect the existence of visibility bias in the distribution of Thomson's gazelle. An alternative approach, based on the regression of group size on the right angle sighting distance was applied to detect the existence of visibility bias.

Population Ecology of Snowy Owls during Winter on the Great Plains of North America

We used data from Christmas Bird Counts (1961-1984) and road counts (1983-1985) to study the winter population ecology of Snowy Owls (Nyctea scandiaca) on the Great Plains of North America. Numbers of owls wintering between 45°N and 53°N increased with latitude. Owl abundance fluctuated from year to year, but fluctuations were not synchronous among count localities across the Great Plains. Owls first appeared on our study sites in southwestern Alberta in early November and individuals continued to arrive until late December or early January. Spring departure occurred during late February and early March, with a few owls remaining until late March. During midwinter, the mean number of owls censused on four study sites ranged from 1.3 to 5.8 owls/100 km in 1983-1984 and from 1.7 to 10.2 owls/100 km in 1984-1985. Although all age-sex classes were represented on the Alberta study areas in both winters, adult birds predominated. Both the Christmas Bird Count data and our fieldwork indicate that owl dispersion is patchy, and that the abundance of owls within patches may vary markedly from year to year. We recommend that future studies of winter raptor populations select multiple study sites to permit detection of patterns that occur over areas larger than a single study site.

Studies of birds in a semi-arid area of Kenya. III The use of ‘Timed Species-counts’ for studying regional avifaunas

ABSTRACT‘Times Species-counts’ are a simple method of comparing the avifaunas of extensive areas by sampling representative habitats. The method has been evaluated in south central Kenya but could be applied to most terrestrial regions of tropical Africa. The essential feature is that the observers move anywhere within a sample site of about 1 km2, recording all of the species seen in a fixed time, e.g. 1 h.Counts are made in all seasons and at various times of day. Reasonable estimates of the total number of species in an area can be derived from a series of 15 counts, but such estimates tend to be low in non-forested habitats because ‘wanderers’ (non-resident species) continue to be recorded almost indefinitely. Open sites have far fewer species than well-wooded areas. The numbers of resident species in non-forested terrestrial habitats is related both to the amount of woody vegetation and to a measure of plant growth. However, total species numbers seem to depend solely on the amount of woody vegetation. Road counts, from a vehicle, were compared to those made on foot. They are less satisfactory, especially for cryptic species.

Turkey Productivity in Two Vegetative Communities in South Texas

Differences in productivity of the Rio Grande turkey (Meleagris gallopavo intermedis) between mesquite (Prosopsis juliflora) and live oak (Quercus virginiana) vegetative communities on the King Ranch in South Texas were investigated from June 6, 1968, to January 3, 1969. The average brood size in August for the mesquite area, as determined from 1,720 poult observations, was 6.9, while 721 poult observations on the live oak area revealed an average brood size of 4.6 The overall poult: hen ratios at this same ffme were 4.7 and 2.6 while the hens seen without poults xrere 31 and 40 percent respectively. The August productivity, or percent of increase in the population due to reproduction, was 336 percent for the mesquite area and 159 for the live oak. The November, or pre-hunting season productivities were 315 and 129 percent. Poult mortality for the 13-week period, between 2 and 15 weeks of age, was calculated to be 22.9 percent for the mesquite area and 12.1 for the live oak. A helicopter census yielded a calculated density of 56 turkeys per 1,000 acres on the mesquite area and 51 on the live oak. Road counts revealed overestimations of these densities ranging from 95-193 percent. Turkey productivity on the King Ranch in South Texas has fluctuated tremendously from year to year. In years of normal precepitation, production has been good, whereas in dry years there has been almost no production of young turkeys ( W. H. Kiel, Jr., personal communication). There are several possible ecological explanations for this situation, all of which may be related to the limited vegetation during dry years. An assessment was made of the turkey productivity in two vegetative communities, mesquite and live oak. This assessment, in two different environments, explored some of the ecological causes of poor turkey productivity. Field work was carried out from June 8, 1968, to January 3, 1969. Turkey densities on the King Ranch have been reported as being considerably greater in live oak than mesquite (Lehmann 1957 ) . In order that the live oak areas maintain higher turkey densities, there must be, through time, either higher productivity, survival, immigration, or some combination of these factors. 1 Research was supported by King Ranch, Inc., University of Wisconsin, and the Ceasar Kleberg Wildlife Foundation. 166 I gratefully acknowledge W. H. Kiel) Jr.7 biologistv King Range, Inc., and R. A. McCabe of the University of Wisconsin for advice, assistance, and editorial help throughout this project. O. J. Rongstad of the University of Wisconsin, provided suggestions in preparing the manuscript.