ABUNDANCE OF SOUTHERN CALIFORNIA COASTAL BOTTLENOSE DOLPHINS ESTIMATED FROM TANDEM AERIAL SURVEYS

We describe a tandem aerial survey method for bottlenose dolphins ( Tursiops truncatus ) that uses two aircraft and independent observer teams to conduct consecutive surveys of the same coastal strip one hour apart. Alternatively, one aircraft with one observer team surveys the same coastal strip twice over several hours. Using mark-recapture analysis, we corrected survey counts for visibility bias resulting from missing dolphin groups at the surface and submerged groups. Dolphin groups were considered "recaptured" when we determined that both observer teams had detected the same group. This tandem method is highly useful for estimating abundance (and visibility bias) for species where population closure may be assumed between flights. We assumed population closure between flights and matched groups using geographic location, group size, and expected travel rates. We derive a new variance estimator of population size which incorporates group-size variability commonly encounteted in cetacean surveys. From six tandem surveys conducted from 1991 to 1994, we estimated the abundance of southern California coastal bottlenose dolphins to be between 78 (95% CI 60-102) and 271 (240-306) animals, with an average of 140 (128-154). Variability in abundance estimates is likely due to seasonal and interannual movement of animals along the California and Baja California coast. Abundance estimates from tandem surveys averaged 53% higher than dolphin counts obtained from individual survey flights, demonstrating the importance of correcting for visibility bias.     

Comparison and Assessment of Aerial and Ground Estimates of Waterbird Colonies

Abstract: Aerial surveys are often used to quantify sizes of waterbird colonies; however, these surveys would benefit from a better understanding of associated biases. We compared estimates of breeding pairs of waterbirds, in colonies across southern Louisiana, USA, made from the ground, fixed-wing aircraft, and a helicopter. We used a marked-subsample method for ground-counting colonies to obtain estimates of error and visibility bias. We made comparisons over 2 sampling periods: 1) surveys conducted on the same colonies using all 3 methods during 3–11 May 2005 and 2) an expanded fixed-wing and ground-survey comparison conducted over 4 periods (May and Jun, 2004–2005). Estimates from fixed-wing aircraft were approximately 65% higher than those from ground counts for overall estimated number of breeding pairs and for both dark and white-plumaged species. The coefficient of determination between estimates based on ground and fixed-wing aircraft was ≤0.40 for most species, and based on the assumption that estimates from the ground were closer to the true count, fixed-wing aerial surveys appeared to overestimate numbers of nesting birds of some species; this bias often increased with the size of the colony. Unlike estimates from fixed-wing aircraft, numbers of nesting pairs made from ground and helicopter surveys were very similar for all species we observed. Ground counts by one observer resulted in underestimated number of breeding pairs by 20% on average. The marked-subsample method provided an estimate of the number of missed nests as well as an estimate of precision. These estimates represent a major advantage of marked-subsample ground counts over aerial methods; however, ground counts are difficult in large or remote colonies. Helicopter surveys and ground counts provide less biased, more precise estimates of breeding pairs than do surveys made from fixed-wing aircraft. We recommend managers employ ground counts using double observers for surveying waterbird colonies when feasible. Fixed-wing aerial surveys may be suitable to determine colony activity and composition of common waterbird species. The most appropriate combination of survey approaches will be based on the need for precise and unbiased estimates, balanced with financial and logistical constraints. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):697–706; 2008)     

THE VALIDITY OF CENSUSING BLACK RHINOCEROS POPULATIONS FROM THE AIR

The efficacy of censusing black rhinoceros ( Diceros bicornis Linnaeus) populations from the air was tested. Repeated aerial counts were made of the black rhinoceros population centered on Qlduvai Gorge, Tanzania, where the number of rhinoceros on the ground is known accurately. Even under the most ideal conditions only 50% of the population was detected by observers in an aircraft, and factors accounting for this are considered. It is concluded that the light aircraft is of limited value in providing estimates of black rhinoceros populations, and estimates based purely on aerial counts are subject to considerable variation.     

Comparison of census methods for black-browed albatrosses breeding at the Ildefonso Archipelago,Chile

A breeding population of black-browed albatrosses has been known to exist at the Ildefonso Archipelago, Chile, for >90 years but the population has never been censused using scientifically defendable methods. To estimate population size, and examine the accuracy and practicality of various census methods, the population was censused in the 2002/2003 breeding season using (a) ground-truthed aerial photography, (b) yacht-based photography, (c) ground counts, (d) quadrat sampling and (e) point-distance sampling. Compared to ground-truthed aerial photography (judged the most accurate) yacht-based photography underestimated population size by 55%, ground counts by 13%, quadrat sampling by 11% and point-distance sampling by 9%. Ground-truthed air photography revealed that in the 2002/2003 breeding season 47,000 pairs of black-browed albatrosses bred at the Ildefonso Archipelago. A repeat aerial census in 2006 suggested the size of the breeding population had not changed in the 4 years between the two censuses. After the Falkland Islands/Islas Malvinas, South Georgia and Diego Ramirez, the Ildefonso Archipelago holds the fourth largest population of black-browed albatrosses in the world.     

Dung survey bias and elephant population estimates in southern Mozambique

We used dung surveys to estimate population size and extracted an age structure from boli diameters for the elephants living in the Maputo Elephant Reserve. Our estimate was based on published defecation rates, dung decay rates, distance-sampling techniques and 1,672 dung piles encountered on 204 line-transects. The reserve had at least 311 (95% CI: 198–490) elephants at a density of 0.60 (95% CI: 0.38–0.94) per km². However, observer bias reduced effective strip widths and inflated estimates and their confidence limits. The age structure extrapolated from dung measurements indicated few newborn calves compared with other populations. To detect population changes of 2–5% at 80% power, dung surveys should be carried out every second year for the next 20 years using 100 transects of at least 500 m each. Comparison with a 1995 dung survey suggests that the population is stable and that previous fears of a major population decline during the civil war have no foundation.     

Die Erfassung von Lachm?wenkolonien durch Luftbilder

Summary Aerial photography was tested for its usefulness to estimate gull populations. The maximal confidence limit between counts of the same colony on different photos was 20.5% (mean: 13%). The conversion factor for calculating the number of nests was 0.84. Ground estimates of the gull population were lower than our results from aerial photography. Changes in the gull populations could be determined by both methods with a tendency in ground samples to overestimate the change. Aerial photography seems to be an appropriate method for quick sampling large gull colonies.     

Technical note: Tree truthing: How accurate are substrate estimates in primate field studies?

Field studies of primate positional behavior typically rely on ground‐level estimates of substrate size, angle, and canopy location. These estimates potentially influence the identification of positional modes by the observer recording behaviors. In this study we aim to test ground‐level estimates against direct measurements of support angles, diameters, and canopy heights in trees at La Suerte Biological Research Station in Costa Rica. After reviewing methods that have been used by past researchers, we provide data collected within trees that are compared to estimates obtained from the ground. We climbed five trees and measured 20 supports. Four observers collected measurements of each support from different locations on the ground. Diameter estimates varied from the direct tree measures by 0–28 cm (Mean: 5.44 ± 4.55). Substrate angles varied by 1–55° (Mean: 14.76 ± 14.02). Height in the tree was best estimated using a clinometer as estimates with a two‐meter reference placed by the tree varied by 3–11 meters (Mean: 5.31 ± 2.44). We determined that the best support size estimates were those generated relative to the size of the focal animal and divided into broader categories. Support angles were best estimated in 5° increments and then checked using a Haglöf clinometer in combination with a laser pointer. We conclude that three major factors should be addressed when estimating support features: observer error (e.g., experience and distance from the target), support deformity, and how support size and angle influence the positional mode selected by a primate individual. individual. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

A CENSUS OF ELEPHANT AND OTHER LARGE MAMMALS IN THE MKOMAZI REGION OF NORTHERN TANZANIA AND SOUTHERN KENYA

• 1. An attempt has been made to census elephant by a method which will enable the reliability of the results to be assessed.
• 2. The method used was a system of stratified random samples.
• 3. Stratification was based on the positions of elephant clumps recorded on a reconnaissance flight.
• 4. Strip samples were selected at random for the various strata and elephant and other large mammals were counted in a strip of 440 m width from an aircraft travelling 100 m above the ground at 130 km/h.
• 5. The problems of maintaining a fixed height above the ground and counting animals in a strip of constant width are acknowledged.
• 6. One stratum was totally counted for purposes of comparison.
• 7. Elephant, eland, kongoni, Grant's gazelle, buffalo, oryx, zebra, impala, ostrich and giraffe have been counted.
• 8. The results are set out in a series of tables and estimates and confidence intervals have been computed.
• 9. A discussion is held on the influences of various factors on the width of sample strips observed from the aircraft.
• 10. The total count and sample count of stratum 1 are observed to be in fairly close agreement.
• 11. The re-stratification of stratum 1 to take advantage of the observed clumps of elephant reduced the standard error of the estimate proportionally. The estimate was increased because the samples were no longer valid for the new strata.
• 12. The elephant population is of the order of 9,000 animals, as was predicted from observation flights, and the confidence interval of ±1,974 is acceptable for a first attempt at a sample count for elephant. The Mkomazi elephant were observed in three distinguishable groups, this being a distribution pattern frequently recorded since 1965.
• 13. Estimates and confidence intervals for other mammals do not refer to the whole region. It is observed that standard errors as a proportion of estimates are proportional to the degree of clumping shown by the species.
• 14. The census took 45 h, and cost K£800. It was accomplished in 7 d by a single pilot and observer. The Mkomazi region covers some 10,857 km².

     

Effects of cross-inoculation from elk and feeding pine needles on the protozoan fauna of pregnant cows: occurrence of Parentodinium africanum in domestic U.S. cattle (Bos taurus)

Consumption of pine needles tends to cause abortion in domestic cattle but not in elk. The present study was undertaken to determine whether this difference was associated with the rumen microbial population. After emptying the rumen, pregnant cattle were inoculated with either elk or cattle rumen contents. For those cows fed the pine needle diet, there was no difference in abortion rate between those inoculated with rumen contents from either elk or cattle. Protozoal concentrations and number of genera were observed to decrease markedly in all cows fed the diet containing pine needles. The cycloposthiid ciliate Parentodinium africanum was observed in rumen contents from several of the domestic cattle (Bos taurus). Concentrations ranged from 1.4 to 130.6 x 10(4) per ml of rumen contents, which comprised 4.6 to 80.3% of the total ciliate population. Mean dimensions of this species were: length, 33.4 microns; width, 19.7 microns; length/width ratio, 1.70, which were similar to those previously reported for this species from Bos indicus in Brazil. This is the first observation of P. africanum, originally observed and described in stomach contents of the hippopotamus, either in Bos taurus or in any host in the northern hemisphere.     

A Double-Observer Method to Estimate Detection Rate During Aerial Waterfowl Surveys

Abstract We evaluated double-observer methods for aerial surveys as a means to adjust counts of waterfowl for incomplete detection. We conducted our study in eastern Canada and the northeast United States utilizing 3 aerial-survey crews flying 3 different types of fixed-wing aircraft. We reconciled counts of front- and rear-seat observers immediately following an observation by the rear-seat observer (i.e., on-the-fly reconciliation). We evaluated 6 a priori models containing a combination of several factors thought to influence detection probability including observer, seat position, aircraft type, and group size. We analyzed data for American black ducks (Anas rubripes) and mallards (A. platyrhynchos), which are among the most abundant duck species in this region. The best-supported model for both black ducks and mallards included observer effects. Sample sizes of black ducks were sufficient to estimate observer-specific detection rates for each crew. Estimated detection rates for black ducks were 0.62 (SE = 0.10), 0.63 (SE = 0.06), and 0.74 (SE = 0.07) for pilot-observers, 0.61 (SE = 0.08), 0.62 (SE = 0.06), and 0.81 (SE = 0.07) for other front-seat observers, and 0.43 (SE = 0.05), 0.58 (SE = 0.06), and 0.73 (SE = 0.04) for rear-seat observers. For mallards, sample sizes were adequate to generate stable maximum-likelihood estimates of observer-specific detection rates for only one aerial crew. Estimated observer-specific detection rates for that crew were 0.84 (SE = 0.04) for the pilot-observer, 0.74 (SE = 0.05) for the other front-seat observer, and 0.47 (SE = 0.03) for the rear-seat observer. Estimated observer detection rates were confounded by the position of the seat occupied by an observer, because observers did not switch seats, and by land-cover because vegetation and landform varied among crew areas. Double-observer methods with on-the-fly reconciliation, although not without challenges, offer one viable option to account for detection bias in aerial waterfowl surveys where birds are distributed at low density in remote areas that are inaccessible by ground crews. Double-observer methods, however, estimate only detection rate of animals that are potentially observable given the survey method applied. Auxiliary data and methods must be considered to estimate overall detection rate.     

Identification of quantitative trait loci affecting cattle temperament

In addition to its potential contribution to improving animal welfare, the study of the genetics of cattle behavior may provide more general insights into the genetic control of such complex traits. We carried out a genome scan in a Holstein x Charolais cross cattle population to identify quantitative trait loci (QTL) influencing temperament-related traits. Individuals belonging to the second-generation of this population (F(2) and backcross individuals) were subjected to 2 behavioral tests. The flight from feeder (FF) test measured the distance at which the animal moved away from an approaching human observer, whereas the social separation (SS) test categorized different activities which the animal engaged in when removed from its penmates. The entire population was genotyped with 165 microsatellite markers. A regression interval mapping analysis identified 29 regions exceeding the 5% chromosome-wide significance level, which individually explained a relatively small fraction of the phenotypic variance of the traits (from 3.8% to 8.4%). One of the significant associations influencing an FF test trait on chromosome 29 reached the 5% genome-wide significance level. Eight other QTL, all associated with an SS test trait, reached the 1% chromosome-wide significance level. The location of some QTL coincided with other previously reported temperament QTL in cattle, whereas those that are reported for the first time here may represent general loci controlling temperament differences between cattle breeds. No overlapping QTL were identified for the traits measured by the 2 different tests, supporting the hypothesis that different genetic factors influence behavioral responses to different situations.     

Realized Sampling Variances of Estimates of Genetic Parameters and the Difference between Genetic and Phenotypic Correlations

A data set of 1572 heritability estimates and 1015 pairs of genetic and phenotypic correlation estimates, constructed from a survey of published beef cattle genetic parameter estimates, provided a rare opportunity to study realized sampling variances of genetic parameter estimates. The distribution of both heritability estimates and genetic correlation estimates, when plotted against estimated accuracy, was consistent with random error variance being some three times the sampling variance predicted from standard formulae. This result was consistent with the observation that the variance of estimates of heritabilities and genetic correlations between populations were about four times the predicted sampling variance, suggesting few real differences in genetic parameters between populations. Except where there was a strong biological or statistical expectation of a difference, there was little evidence for differences between genetic and phenotypic correlations for most trait combinations or for differences in genetic correlations between populations. These results suggest that, even for controlled populations, estimating genetic parameters specific to a given population is less useful than commonly believed. A serendipitous discovery was that, in the standard formula for theoretical standard error of a genetic correlation estimate, the heritabilities refer to the estimated values and not, as seems generally assumed, the true population values.     

Demography and nesting ecology of green iguana, Iguana iguana (Squamata: Iguanidae), in 2 exploited populations in Depresión Momposina, Colombia

We studied the demography and nesting ecology of two populations of Iguana iguana that face heavy exploitation and habitat modification in the Momposina Depression, Colombia. Lineal transect data was analyzed using the Fourier model to provide estimates of social group densities, which was found to differ both within and among populations (1.05-6.0 groups/ha). Mean group size and overall iguana density estimates varied between populations as well (1.5-13.7 iguanas/ha). The density estimates were far lower than those reported from more protected areas in Panama and Venezuela. Iguana densities were consistently higher in sites located along rivers (2.5 iguanas/group) than in sites along the margin of marshes, probably due to vegetational differences (1.5 iguanas/group). There was no correlation between density estimates and estimates of relative abundance (number of iguanas seen/hour/person) due to differing detectabilities of iguana groups among sites. The adult sex ratio (1:2.5 males:females) agreed well with other reports in the literature based upon observation of adult social groups, and probably results from the polygynous mating system in this species rather than a real demographic skew. Nesting in this population occurs from the end of January through March and hatching occurs between April and May. We monitored 34 nests, which suffered little vertebrate predation, perhaps due to the lack of a complete vertebrate fauna in this densely inhabited area, but nests suffered from inundation, cattle trampling, and infestation by phorid fly larvae. Clutch sizes in these populations were lower than all other published reports except for the iguana population on the highly xeric island of Cura?ao, implying that adult females in our area are unusually small. We argue that this is more likely the result of the exploitation of these populations rather than an adaptive response to environmentally extreme conditions.     

Comparative analysis of visual census techniques for highly mobile,reef-associated piscivores (Carangidae)

Synopsis Visual census techniques applicable to coral reef-associated fishes are reviewed and the results of field tests using six (three transect-based and three point-based) to estimate the density of carangids at Carter Reef, Great Barrier Reef, are presented. Data are analyzed with respect to the effects of observers on fishes seen, observer biasses, precision of the estimates and, as far as possible, accuracy of the estimates. Transects generate estimates of population density and structure different from those of point-based estimates. Various point-based census methods, however, generate density estimates consistent with one another and are generally more precise than transect-based methods. The results of the field study obviously cannot be generalized to other quite different types of reef fishes. The problems we encountered and a review of the techniques used to census reef fishes visually in the past, however, suggest that: (1) interval counts, such as Rapid Visual Census techniques, are likely to be inaccurate and difficult to compare; (2) for species with high probabilities of detection, instantaneous area counts appear to be the most effective way to estimate densities, whereas cryptic species are best censused using instantaneous variable distance point counts, and (3) strip transects may often be less efficient than line transects, due to inconstant levels of subject detectability.     

Estimation of walrus populations on sea ice with infrared imagery and aerial photography

Population sizes of ice‐associated pinnipeds have often been estimated with visual or photographic aerial surveys, but these methods require relatively slow speeds and low altitudes, limiting the area they can cover. Recent developments in infrared imagery and its integration with digital photography could allow substantially larger areas to be surveyed and more accurate enumeration of individuals, thereby solving major problems with previous survey methods. We conducted a trial survey in April 2003 to estimate the number of Pacific walruses (Odobenus rosmarus divergens) hauled out on sea ice around St. Lawrence Island, Alaska. The survey used high altitude infrared imagery to detect groups of walruses on strip transects. Low altitude digital photography was used to determine the number of walruses in a sample of detected groups and calibrate the infrared imagery for estimating the total number of walruses. We propose a survey design incorporating this approach with satellite radio telemetry to estimate the proportion of the population in the water and additional low‐level flights to estimate the proportion of the hauled‐out population in groups too small to be detected in the infrared imagery. We believe that this approach offers the potential for obtaining reliable population estimates for walruses and other ice‐associated pinnipeds.     

植草带宽度对蜘蛛和步甲群落动态及比邻玉米田害虫发生的影响

农田边界植草带是农田系统各斑块间生物物种迁移和群落演替、物质和能量交换的主要区域,对维持农业生物多样性及提高农田生产力具有重要意义。基于作物-害虫-天敌互作有机整体对植草带宽度的响应,选取不同宽度植草带(2 m、4 m、6 m)及其比邻农田并以对应宽度作物边界作为对照,采用地表陷阱法对蜘蛛和步甲进行取样调查,探究植草带宽度对蜘蛛和步甲种群结构、迁移扩散规律以及对农田害虫控制潜力的影响。结果表明:植草带内蜘蛛和步甲个体数均显著高于对照条带,4 m、6 m植草带的蜘蛛和步甲多度显著高于2 m植草带,且物种丰富度和多度显著高于其对照条带。此外,不同宽度植草带蜘蛛和步甲群落存在较高的异质性,蜘蛛和步甲群落结构差异显著;在4 m和6 m植草带及其比邻玉米田内,蜘蛛和步甲多度在植草带和植草带与比邻玉米田交界处显著高于农田内部,且随距离的增加,蜘蛛物种多度呈显著降低趋势,植草带宽度和距离共同决定蜘蛛和步甲的空间分布;Monte Carlo检验结果表明,植草带宽度、植被Margalef指数对农田中蜘蛛和步甲群落结构的影响均达到显著水平,蜘蛛主要优势科和步甲主要优势种主要分布在6 m植草带比邻玉米田内;4 m、6 m植草带比邻的玉米田中蜘蛛和步甲对玉米害虫的益害比显著高于2 m植草带比邻的玉米田,且4 m、6 m植草带显著增加了玉米籽粒的百粒重及比邻农田的玉米总产量。本研究对植草带涵养捕食性天敌预防害虫发生的最适宽度进行探索,综合考虑植草带耕地占用、天敌涵养和生物控害潜力等因素,确定4 m宽度植草带是具有推广价值的农田边界模式。     

AERIAL CENSUS OF BLACK RHINOCEROS USING STRATIFIED RANDOM SAMPLING

During 1967–1968 a census was conducted of the black rhinoceros (Diceros bicornis L.) population in part of the Tsavo ecological unit. The region concerned covers an area of approximately 23,300 km² (9,000 square miles). Large parts of the region were systematically covered in a light aircraft and all rhinoceros observed were recorded on a 1:250,000 map. Because of the visibility bias inherent in such censuses correction factors were placed on the raw aerial data and crude estimates obtained. These crude estimates were then checked by intensive work on the ground in several sectors, and adjustments made where necessary. Using these crude estimates approximately two-thirds of the area under consideration were stratified into five density strata: very high, high, medium, low, and very low. Within this area 250 randomly located 2.59 km² (1 square mile) plots were intensively searched from the aircraft and all rhinoceros observed on these plots recorded. In the very high, high, and medium density strata these intensive searches resulted, at the 95% level of significance, in a population estimate of 4,200±25% of the mean or an estimate of between 3,150 and 5,255 rhinoceros within these strata. In the low stratum the statistical analysis resulted in a population estimate of 306±83% of the mean or an estimate of between 47 and 565 rhinoceros at the 90% level of significance. In the very low stratum the population estimate, at the 50% level of significance, was 266 ± 50% of the mean or an estimate of between 133 and 400 rhinoceros. A comparison of the crude estimates and the refined statistical estimates illustrates close agreement. The remaining third of the area was covered systematically and correction factors were placed on the raw aerial data. Crude estimates suggest a population of 2,800–3,000 occupying this part of the area. Assuming that this crude estimate, together with the statistical estimates for the low and very low strata, are rough approximations of the actual populations, it is statistically probable that the true population of black rhinoceros in this region lies between 6,130 and 9,220.     

Conducting animal censuses amongst abrupt topography; a GIS‐based alternative to Distance

Management often bases decisions on estimates of animal density and population size. Aerial sampling is expensive whilst current ground methods, noticeably Distance sampling, assume a single detection function for each habitat and that visibility in a given habitat type declines in a smooth, increasing manner with distance from the observer. If the visibility within a habitat varies widely or is suddenly cut off, as amongst abrupt topography, these assumptions are invalidated. We present an affordable, accessible and accurate method for conducting repeated annual censuses on large herbivores in such terrain. We used a GIS habitat‐based approach. Monthly, over a two year period, we conducted repeated road transects in Ithala Game Reserve, South Africa, using GPS to record the geographic position of each sighting. These records (n = 8742) were then imported into a GIS and overlaid onto an existing habitat‐type GIS layer. With the sampled area thus defined as an irregular polygon in the GIS encompassing all records, we calculated densities of each herbivore species by habitat type and extrapolated total population size estimates. Estimates of maximum population size for wildebeest and zebra correlated (±15%) with management's estimates based on aerial surveys, walked transects and experience. White rhino are individually counted in the reserve and our estimates (year 1: 52; year 2: 57) matched these known numbers (year 1: 50; year 2: 53). Our method also yielded realistic numbers for impala, but unrealistic numbers for kudu and warthog. Our GIS‐based census technique produced realistic maximum population estimates for abundant grazing and mixed‐feeder mesoherbivores and for scarce, but highly visible, megaherbivores, but not for cryptic species. With the increasing availability of GIS data, the technique is recommended to those working in abrupt terrain frustrated by the inability of current ground census techniques, principally Distance sampling, to produce realistic population estimates.     

Performance of ground-based and aerial survey methods for monitoring wildlife assemblages in a conservation area of northern Tanzania

Validating and improving field-sampling techniques for estimating wildlife community composition and population size is essential for wildlife management and conservation. We conducted ground distance sampling surveys along line transects and block counts from a small aircraft in Manyara Ranch in Northern Tanzania and contrasted estimates of species richness and species-specific densities from both sampling techniques. We used regression analyses (logistic regression and generalized linear mixed models) and model selection to investigate whether a species’ body size, group size, body color, as well as vegetation cover explained the variation in species presence/absence and relative density differences in aerial vs. ground-based sampling. Ground surveys detected significantly more species than aerial surveys. However, aerial surveys detected three species that were missed by ground surveys (African lions, African buffalo, and spotted hyena). Model selection suggested that species with smaller body mass and small group sizes were more likely to be missed in aerial surveys. Densities estimated from the aerial surveys were generally but non-significantly lower than the densities estimated from the ground surveys, with the exception of density estimates for African elephants which were slightly higher from aerial surveys. Density differences between the two methods were greater for species with small group size, light body color, and in areas with denser vegetation cover; these variables explained 75% of the variation in density differences between the two survey methods. Albeit being similar in operational costs in our relatively small study area, ground surveys yielded (1) more complete information with respect to wildlife community composition and (2) density estimates were mostly higher and (3) more precise and (4) appear more feasible to be implemented in community-based conservation schemes.