The relationship between soil variables and leafcutter ant (Atta sexdens) nest distribution in the Colombian Amazon

We determined the relationships between several soil variables and the distribution of leafcutter ant (Atta sexdens) nests on the Colombian shore of the Amazon River. Seven habitats were identified in which nests were consistently present or absent. Soil samples for physiochemical analysis were taken near nest sites in three habitats where nests were present and from randomly selected sites in four other habitats where nests were absent. Percent canopy cover and soil resistance were also measured for each site. Almost all of the 20 identified soil variables were significantly different between habitats with and without A. sexdens nests, and the values of all variables were heterogeneous between the seven habitats. The most important variables correlated with leafcutter ant nest presence were percent canopy cover (positively), percent silt, soil resistance at 0–20 cm, and pH (all negatively). We deduced a binomial and a multinomial logistic regression which showed how each of these variables was related to nest presence and habitat, respectively. We describe how each variable may affect leafcutter ant nest development, especially in its earliest stages, and therefore influences nest distribution. We propose a suitable-soil hypothesis which, complementary to the palatable forage hypothesis, aims to explain patterns in leafcutter ant nest demography based on soil conditions.     

Survey of Neodohrniphora spp. (Diptera: Phoridae) at colonies of Atta sexdens rubropilosa (FOREL) and specificity of attack behaviour in relation to their hosts

Atta sexdens rubropilosa is a leaf-cutting ant that is a significant agricultural and forestry pest in the Neotropical region. This ant is parasitized by flies from the genera Neodohrniphora spp., Apocephalus spp. and Myrmosicarius spp. This study was carried out to determine which species of Neodohrniphora spp. are found near foraging trails of Atta sexdens rubropilosa and to evaluate the specificity of attack behaviour of these parasitoids. From May 2002 to April 2004, we sampled Neodohrniphora spp. hovering over foraging trails of Atta sexdens rubropilosa between 8:00 and 11:00 h and between 15:00 and 18:00 h. To investigate the attacking behaviour against the ants, flies were released individually inside an observation chamber containing a single leaf-cutting ant worker. Each parasitoid was confronted successively with a worker ant of A. sexdens rubropilosa, Atta laevigata Smith, Acromyrmex crassispinus Forel and Acromyrmex subterraneus molestans Santschi. Phorids of three species were identified: Neodohrniphora elongata Brown, Neodohrniphora declinata Borgmeier and Neodohrniphora tonhascai Brown. The three phorid species were active throughout the year and often along the same foraging trails, but N. elongata was the most frequent species. In the laboratory assay, N. elongata, N. declinata and N. tonhascai attacked workers of A. sexdens rubropilosa, A. laevigata and A. crassispinus, but not of A. subterraneus molestans.     

Persisting Hyper-abundance of Leaf-cutting Ants (Atta spp.) at the Edge of an Old Atlantic Forest Fragment

Leaf-cutting ants (LCAs) profoundly benefit from edge creation in Neotropical forests, where they act as a keystone species and disturbance agent. In view of their poorly explored population dynamics, the question arises whether high densities of LCAs are a transitional or a persisting phenomenon. We studied the temporal variation of LCA colony densities at the edge of the Brazilian Atlantic forest. At physically stable edges of an old forest fragment, densities of Atta cephalotes and Atta sexdens (11 and five times higher in a 50 m edge zone in comparison with the forest interior) persisted over a 4-yr interval (2001–2005) with no significant difference in densities between years. Species-specific per colony growth rates ranged from 12 to −5 percent/yr, suggesting that populations were approximately at equilibrium. High rates of colony turnover (little less than 50% in 4 yr) indicated an average colony life span of about 7 yr—a life expectancy considerably lower than previous estimates for Atta colonies. Stable, hyper-abundant populations of LCAs accord with the constantly high availability of palatable pioneer vegetation (the preferred food source of LCAs) at forest edges and are expected to persist in time as long as forests are characterized by high edge to interior ratios, with potentially long-lasting consequences for the ecosystem.     

Comparative morpho-physiology of the metapleural glands of two Atta leaf-cutting ant queens nesting in clayish and organic soils

Queens of leaf-cutting ants found their nests singly, each consisting of a vertical tunnel and a final horizontal chamber. Because of the claustral mode of nest founding, the queen and/or her initial fungus garden are exposed to threats imposed by several soil pathogens, and the antibiotic secretions produced by their metapleural glands are considered a main adaptation to deal with them. Nests of two Atta leaf-cutting ant species, Atta vollenweideri and Atta sexdens rubropilosa, occur in different soil types, alfisols and oxisols. Their queens are known to excavate the initial nest in different soil horizons, clayish and organic, respectively, which differ in their fertility and associated microbiota. The aim of the present study was to comparatively investigate the morpho-physiology of the metapleural glands in queens of A. vollenweideri and A. sexdens rubropilosa, addressing the question whether the distinct selective pressure imposed by the microbiota in the two different soil types led to morpho-physiological differences in the metapleural glands that were consistent with their antiseptic function. The results revealed that metapleural glands of A. sexdens rubropilosa have a larger number of secretory cells, and consequently a higher production of antibiotic secretions, which may have been selected to allow nest founding at the superficial horizon of oxisols rich in organic matter and microorganisms. Glands of A. vollenweideri, on the contrary, presented fewer secretory cells, suggesting less production of antibiotic secretions. We argue that the excavation of deep founding nests in A. vollenweideri was primarily selected for during evolution to avoid the risk posed by flooding, and further hypothesize that a reduced number of cells in their metapleural glands occurred because of a weak pathogen-driven selective pressure at the preferred soil depth.     

Developmental changes in factors limiting colony survival and growth of the leaf‐cutter ant Atta laevigata

Many species of leaf‐cutter ants (Atta and Acromyrmex) increase in abundance following natural or anthropogenic disturbances in the vegetation. However, the mechanisms responsible for such an increase are still poorly understood. We evaluated the effects of nesting site and the availability of palatable forage on survival and growth of Atta laevigata colonies at different developmental stages. Foundress queens transplanted into man‐made clearings (dirt roads) had a much higher survival than those transplanted into the adjacent undisturbed savannah vegetation. Similarly, incipient colonies (≥3‐months old) had significantly greater survival and growth rates in dirt roads. In contrast, nesting site did not influence performance of young colonies (≥15‐months old). Both incipient and young colonies responded strongly and positively to experimental supplementation of palatable forage, and this effect was independent of the nesting habitat. Colonies that received extra food grew faster and had a significantly greater survival rate than control colonies. These results suggest that performance of A. laevigata is affected by the generally greater availability of suitable nesting sites and palatable vegetation in disturbed habitats. This may explain how these ants maintain high densities in these habitats, and since the relative importance of these factors changed with colony ontogeny, our findings highlight the importance of evaluating potential limiting factors throughout the full range of an organism's developmental stages.     

Ecosystem engineering by leaf‐cutting ants: nests of Atta cephalotes drastically alter forest structure and microclimate

1. The role played by Atta species as ecosystem engineers remains poorly investigated despite previous evidence that their nests can impact plant assemblages. 2. In a large remnant of Atlantic forest, we compared forest structure at 36 Atta cephalotes nests to control sites and assessed shifts in microclimate along transects from nests up to 24 m into the forest (11 representative colonies). 3. Nests (average size: 55 m²) were virtually free of understorey vegetation with a high proportion of dead stems (up to 70%). 4. Canopy openness above colonies increased by roughly 40% compared with controls (5.3% at colony vs. 3.7% at control sites). 5. At nest centres, about 6% of the total radiation penetrated through the sparse canopy. Light levels declined exponentially, reaching a third (2%) in the unaffected forest understorey. 6. Likewise, maximum soil temperatures and daily amplitudes declined exponentially from 25 to 23 °C and 1.6 to 0.8 °C, respectively. Soil moisture increased significantly along transects, yet the effect was small and no differences were detected for air temperature and humidity. 7. We extrapolated that individual A. cephalotes nests modify the microclimate in an area of almost 200 m² on average. For the population, this amounts to 6% of the area along forest edges, where colonies are strongly aggregated, compared with only 0.6% in the forest interior. 8. Nests changed microclimate to an extent that has been reported to impact seed germination, plant growth, and survival of seedlings, conclusively demonstrating that leaf‐cutting ants act as ecosystem engineers.     

Nest Predation Risk on Ground and Shrub Nests in Forest Margin Areas of Sulawesi, Indonesia

Forest loss and fragmentation in Indonesia may seriously affect the survivorship of forest birds and lead to local extinction of bird populations. We used 786 artificial nests baited with quail eggs to examine the effect of habitat alteration on nest predation in Lore Lindu National Park, Sulawesi. Natural forest and four habitats of forest margin areas: forest edge, forest gardens, coffee plantations, and secondary forest, were studied. Two types of artificial nests, ground and shrub nests were placed in these habitats at two different locations for a period of 8 days. In addition, we used automatic cameras and cage-traps to identify the predators. Nests in shrubs experienced significantly higher predation rates in forest margin areas than in natural forest. Predation on ground nests did not differ significantly between these habitat types, but was significantly higher than that on shrub nests in each habitat except forest edge. Rodents were the most common predators of both nests, but shrub nests were also susceptible to Dwarf cuscus (Strigocuscus celebensis), squirrels, and tree snakes. The nest predation rates we found were among the highest found in tropical rainforests, probably a consequence of the unique predator assemblages of Sulawesi. These results suggest that egg survival is negatively affected by human intervention and that human-induced habitats might have only limited importance for the conservation of Sulawesi's largely endemic understorey avifauna. These considerations might be important since forest margins comprise significant proportions of protected areas on Sulawesi and play an important role in future Park zoning concepts as well as in conservation-oriented land use management.     

Simple and farmer-friendly bumblebee conservation: Straw bales as nest sites in agricultural landscapes

Many bumblebee species are declining due to a loss of semi-natural habitats in agricultural landscapes resulting in diminished forage and nest sites. Anecdotal experience indicates that bumblebees nest in straw bales, but scientific evidence is lacking. We spent 250 h screening for bumblebee nests in 1255 straw bales and ten straw stacks belonging to 58 farms in two intensively farmed Swedish regions and recorded nests, nest traffic, and straw characteristics. We supplemented the straw screening with screening of control areas, without straw, that were selected in similar environments as the areas with straw. We observed 45 bumblebee nests (including potential nests where a single bumblebee flew in or out of the straw) of eight species/species groups, including one red-listed, in or directly adjacent to the straw at 26 of the farms. Nests were mainly found in partly decayed straw and bales placed together. We found no nests in control areas. Based on our results, we suggest that straw can be used as an easy, cheap and efficient intervention to increase the availability of bumblebee nest sites in agricultural landscapes. Considering the costs and benefits of the alternatives, we conclude that straw addition has advantages over commercial bumblebee colonies for crop pollination purposes and over artificial nest boxes for conservation purposes.     

Location of bumblebee nests is predicted by counts of nest‐searching queens

1. Bumblebee nests are difficult to find in sufficient numbers for well replicated studies. Counts of nest‐searching queens in spring and early summer have been used as an indication of preferred nesting habitat, but this relationship has not yet been validated; high densities of nest‐searching queens may indicate habitat with few nesting opportunities (meaning that queens have to spend longer looking for them). 2. From mid April 2010, queen bumblebees were counted along 20 transects in grassland and woodland habitats in central Scotland, U.K. The number of inflorescences of suitable forage plants were also estimated at each transect visit. The area surrounding each transect was searched for nests in the summer. 3. In total, 173 queen bumblebees were recorded on transects, and, of these, 149 were engaged in nest‐searching. Searches subsequently revealed 33 bumblebee nests. 4. The number of nest‐searching queens on transects was significantly, positively related to the number of nests subsequently found. Estimated floral abundance along the transect did not correlate with numbers of nest‐searching queens or with the number of nests found, suggesting that queens do not target their searching to areas that are locally high in spring forage. 5. The data suggest that counts of nest‐searching queens provide a useful positive indication of good nesting habitat, and hence where bumblebee nests are likely to be found later in the year.     

Why are leaf‐cutting ants more common in early secondary forests than in old‐growth tropical forests? An evaluation of the palatable forage hypothesis

I evaluated the hypothesis that leaf‐cutting ants are more common in early successional forests than in old‐growth forests because pioneer species, which dominate in early successional habitats, appear more susceptible to leafcutters than shade‐tolerant species, which dominate primary forests (palatable forage hypothesis). The relative importance of pioneer and shade‐tolerant species as plant resources for leaf‐cutting ant colonies was evaluated (1) by literature review of leaf‐cutting ants’ diet, and (2) experimentally, using field assays to determine leafcutter's selectivity. Pioneer species were harvested three times more frequently than shade‐tolerant species and made up the largest component of the diet in all the studies reviewed. The amount harvested was not correlated with the plant species abundance. In addition, leaves from pioneer plants were selected eight times more than leaves from shade‐tolerant species in the field assays. These results support the palatable forage hypothesis. Leafcutters probably select pioneer leaves because of their low level of chemical defenses and high nutrient content. The high availability of pioneer species in early successional forest probably decreases the cost to locate palatable resources. Therefore, early successional habitats support more ant colonies than old‐growth forests. On the other hand, the effective defense mechanisms of mature plant species and the high dispersion of palatable plants could explain the low density of leaf‐cutting ant colonies in old‐growth forests. The palatable forage hypothesis is compared with other hypotheses that explain leaf‐cutting ant density. The preference of foundress queens for forest clearings, the dependence of small colonies on herbs, and the importance of pioneer plant species for mature colonies (palatable forage hypothesis) can be considered complementary, because they focus on different stages of the colony's life history. Consequently, the availability of pioneer plants appears to be one of the most influential factors determining mature leaf‐cutting ant nest densities in Neotropical forests.     

Leaf-cutting ant nests support less dense and impoverished seed assemblages in a human-modified Caatinga dry forest

Regenerating forests make up an increasingly large portion of tropical landscapes worldwide and regeneration dynamics may be influenced by leaf-cutting ants (LCA), which proliferate in disturbed areas and collect seeds for fungus culturing. Here, we investigate how LCA influences seed fate in human-modified areas of Caatinga dry forest. We evaluate the seed deposition and predation on Atta opaciceps nests, foraging habitat surrounding nest and control habitat away of nest influence of 15 colonies located along a forest cover gradient during the rainy and dry seasons. For each habitat, four 50-cm² plots were established and all seeds on the soil surface were collected along 1 year. We recorded 13,628 seeds distributed among 47 species and 36.57% of the total seeds did not show any sign of predation. Nest mound habitats supported low-density and species-poor seed assemblages, which were taxonomically distinct from the control habitats. These effects only occurred in the rainy season. The proportion of undamaged seeds were similar across the habitats. While forest cover did not influence seed assemblage in terms of species richness or seed predation, it did interact with habitat type via increments in seed abundance as forest cover increased across the nests. Forest cover also affected seed composition, but only in the rainy season. These results indicate that LCA decrease seed deposition in areas under their influence, particularly on the nest mounds. As LCA profit from human disturbance in the Caatinga, their role as seed ‘sinks’ should be enhanced in disturbed Caatinga patches, particularly during the rainy season, when most of the plant recruitment occurs. Our findings reinforce the importance of LCA as drivers of forest dynamics and resilience in human-modified landscapes.     

Nesting Habitat of the Lilac-crowned Parrot in a Modified Landscape in Mexico

Parrot populations are being increasingly pressured to occupy modified or fragmented landscapes, yet little is known of the habitat requirements of most species, particularly with regard to the effects on breeding habitat. We evaluated nesting habitat of the lilac-crowned parrot Amazona finschi in the modified landscape of coastal Michoacan in Mexico. We located 90 parrot nests in 12 tree species in Michoacan, with lilac-crowned parrots presenting a narrow niche-breadth of tree species used for nesting. Considering an additional 82 nest trees recorded for lilac-crowned parrots in Jalisco, we determined a 51 percent similarity in cavity resource use by parrots in the two dry forest regions. Overall, the predominant nest tree species with 76 percent of nests were Astronium graveolens , Piranhea mexicana , Brosimum alicastrum , and Tabebuia spp., all characteristic of semi-deciduous forest. Only 8 percent of nests occurred in trees characteristic of deciduous forest. Parrots utilized large trees with canopy level cavities as nest sites, and preferred conserved semi-deciduous forest for nesting, with fewer nests than expected in deciduous forest and transformed agricultural land. Nest areas in semi-deciduous forest occurred on significantly steeper terrain, as remnant semi-deciduous forest is restricted to steep ridges and canyons. Those parrot nests in modified habitats and forest patches were located near to continuous forest, with nest trees in open agricultural land being significantly closer to continuous forest than nests in disturbed forest patches. These results demonstrate the importance of conserved semi-deciduous forest as breeding habitat for the threatened, endemic lilac-crowned parrot, making wild populations of the species vulnerable to the high rate of transformation and fragmentation of tropical dry forest.     

Population Density of Chimpanzees and Gorillas in the Petit Loango Reserve,Gabon: Employing a New Method to Distinguish Between Nests of the Two Species

We studied the vegetation and population density of chimpanzees (Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) in the Petit Loango Reserve, Gabon. The study site consists mainly of primary and secondary forest, and it also includes patches of savanna, inundated forest, and coastal scrub. The density of herbaceous plants of Marantaceae and Zingiberaceae, which serve as important foods for great apes at other study sites, is extremely low. It was very difficult to distinguish between the nests of chimpanzees and gorillas because most gorilla nests were made in trees. We developed a new method to identify the builder of nests via a combination of field observation of nests and fecal samples, and examination of hair samples under a scanning electron microscope. Nests of chimpanzees were mainly in primary forest, and the estimated density (0.78 individual per km ² ) is higher than the average density in Gabon and comparable to the nest density in the Lopé Reserve, Gabon. Nests of gorillas were mainly in secondary forest, and their estimated density (0.21) is similar to the average next density in Gabon but lower than the gorilla nest density in the Lopé Reserve. The low density of herbaceous foods seemed to influence the density of gorillas but not the density of chimpanzees.     

Predation on artificial nests in a forest dominated landscape – the effects of nest type, patch size and edge structure

We studied the effects of forest patch size and forest edge structure on nest predation in a boreal coniferous forest landscape. The following predictions were tested. Nest predation should be higher in small than in large stands, in edges than in interior areas of forest stands, and in barren forest/clear–cut edges created by forestry than in natural forest/open marsh edges. Four types of artificial above ground nests (total of 261) were used; open cup nests with reindeer Rangifer t. tarandus hair, open cup nests with domestic hen Gallus domesticus feathers, and unlined open cup and nest–box nests. Nests were baited with one Japanese quail Coturnix coturnix japonica egg. Nest–boxes were depredated significantly less than open cup nests of all types. No edge- or stand size–related nest predation was found. The predation rate, regardless of the nest type, did not differ relative to the edge type and vegetation characteristics. However, better horizontal visibility of open cup nests due to more open vegetation structure increased predation risk in man–made edges compared to inherent edges. The results suggest that edge–related nest predation is absent or weak in forest dominated landscapes. This may be due to predator types present in the landscape and/or predators habitat use in forest dominated areas. Therefore, it might be that findings documented in other areas, such as in agricultural dominated landscapes, cannot be directly applied to managed forest landscapes.     

Artificial nest predation in hedgerows and scrub forest in a human-dominated landscape of central Mexico

Hedgerows as well as other narrow corridors could be valuable habitats for birds in regions of intensive agriculture, however, it is still not clear how successful breeding birds are in different types of hedgerows as compared to birds nesting in their natural habitats. We used artificial nests to examine whether hedgerows were sinks (ecological traps) for birds by comparing rates of predation in two types of hedgerows with different vegetation structure (simple and complex), and in a tract of scrub forest in an agricultural landscape of central Mexico. We determined also the types of predators responsible for egg predation. Ground and elevated nests were baited with one Japanese quail Coturnix japonica egg and one plasticine egg and placed alternately along transects. Significantly, greater predation rates were found in scrub forest and complex hedgerows than in simple hedgerows. Higher predation rates in complex habitats seemed to reflect the higher number of predator types found there. The most important predator types were carnivores followed by rodents, birds, and humans. Carnivores and rodents mainly predated ground nests, whereas birds and humans predated elevated nests. Simple hedgerows in this landscape appeared to offer relatively safe nest sites in terms of predation pressure when compared to more complex habitats (complex hedgerows and scrub forest).     

Population consequences of huge nesting aggregations ofRopalidia plebeiana (Hymenoptera: Vespidae)

Nest survival rates and reproductive rates of females of the Australian paper wasp, Ropalidia plebeiana, in nest aggregations under a concrete bridge were studied. The annual colony cycle commenced in August with the reutilization of old nests and by the founding of new nests, mainly by associations of foundresses. Distribution patterns of the number of foundresses per nest was nearly random on new nests while contagious on old nests. About one-third of the increase in number of nest was achieved by dividing large, old nests and two-thirds by founding new nests. Nest survival rates for old nests (August to April) and new nests (November to April) were 89.6% and 88.8% respectively, far higher rates than those of other polistine wasps so far reported. The numbers of nests and reproductive females increased during a colony cycle by 2.30 and 10.98 times, respectively. Thus, huge aggregations of nests are probably beneficial for this species by enabling the realization of high reproductive rates. We could find no density-dependent effect in nest growth rate or production of female reproductives. Ratio of cells parasitized by ichneumonid wasps was low. Nests in the central part of an aggregation were prasitized at significantly lower rates than nests on the periphery or scattered nests outside a dense aggregation, suggesting a selfish herd effect.     

Effects of Forest Type and Human Presence on Bonobo (Pan paniscus) Density in the Salonga National Park1

Our study elucidates how forest type characteristics and human presence influence bonobo (Pan paniscus) densities and assesses whether the Salonga National Park harbors a substantial bonobo population. We searched 11 locations in the Salonga for the presence of bonobos and sampled 9 study sites using line transects to estimate relative bonobo nest density, the proportion of forest types, and the intensity of human activity. We classified forests into broad types by overstory and understory composition, canopy cover, and hydrology, and calculated encounter rates for bonobo, human, and large mammal signs. Bonobo signs occurred in 8 of 11 locations but varied widely in frequency. Mean density was 0.72 nest-builders/km², but density was not uniform across sites (range=0–2.8 nest-builders/km²). Of 11 forest types encountered, the most common were mixed mature forest with an herbaceous (Marantaceae) understory (36.8%), with a woody understory (23.6%), and old secondary forest with a Marantaceae understory (10.5%). Nest sites occurred only in these forest types, called nest-forest types. Bonobo density was highest in locations comprising >80% nest-forest types. Nests occurred more frequently in the mixed mature/Marantaceae forest. Nest-site density correlates positively with the nest-forest patch length we encountered on transects, implying that forest patch size and consistency may influence bonobo density. Mean nest group size correlates positively with proportion of nest-forest types found at a site, suggesting that increased resource availability—nesting sites and food—allows larger group size. A significant inverse association existed between bonobo density and human presence. An erratum to this article can be found at     

Location matters: survival of artificial nests is higher in small grassland patches and near the patch edge

Nest survival is an important part of breeding success in grassland ecosystems, and the location of nests can determine vulnerability to different predators. We conducted an experiment with artificial nests to evaluate jointly the predation rate on nests at different spatial scales (landscape, patch and tussock) and the relative abundance of potential nest predators (small mammals and birds) in a temperate grassland area. In November 2014 and 2016, we installed 288 artificial nests in Common Pampas Grass Cortaderia selloana grasslands in the southeastern Pampas region, Argentina. The nests were placed in two 10-ha plots in a continuous grassland patch (c. 900 ha) within a reserve and in two small grassland patches (1.5 and 1.8 ha) in an agricultural matrix (landscape-scale), at the patch edge and inside the patches (patch-scale), and at two heights within the tussock grass (tussock-scale). In 2016, we also conducted live trapping of small mammals and surveyed birds along strip transects at the sampling sites. Nests located in patches within an agricultural matrix and near the edge had greater relative survival than those set in the reserve and inside the patches, respectively. This might be explained by the lower relative abundance of small mammals that we found outside the reserve. Artificial nest survival values recorded at the landscape-scale contrasted with those previously observed for natural nests. Our results could be partly explained by differences in nest density between agro-patches and those within the reserve. Future studies could also evaluate the role of parental nest defence on nest survival.     

Leaf‐cutting ants as ecosystem engineers: topsoil and litter perturbations around Atta cephalotes nests reduce nutrient availability

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Predation of artificial nests by introduced rhesus macaques (<Emphasis Type="Italic">Macaca mulatta</Emphasis>) in Florida,USA

Native throughout Asia, rhesus macaques are believed to have the widest native range of any non-human primate and are capable of adapting to an extensive diversity of habitats. Rhesus macaques have caused environmental degradation in introduced habitats, including decreasing bird populations through nest predation. In the 1930s, rhesus macaques were intentionally introduced into what is today Silver Springs State Park (SSSP), central Florida, in an effort to increase tourism. Our objective was to determine whether introduced rhesus macaques in SSSP would consume eggs presented in artificial nests. We used camera traps adjacent to 100 open-cupped artificial bird nests baited with quail eggs near the Silver River. Nests were placed in shrubs and left in the field site for 12 days, representative of the incubation period of native passerine species. Twenty-one nests were depredated by rhesus macaques, nine by nest predators other than macaques, and five nests by an unidentified predator. Nests were more likely to be depredated by macaques when located in areas of high macaque relative abundance. This study suggests introduced rhesus macaques may influence nest predation rates of native bird species in natural areas.