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The bat fauna of Tambito, Colombia

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This paper summarizes a first account of the bat fauna in the middle elevations of the Tambito Nature Reserve in the Colombian Chocó. A month-long survey using mist netting found 13 genera comprising at least 26 species. As expected from mist net bias, virtually all the bats captured were understory phyllostomids, with few exceptions. Nonetheless, high ecological diversity was confirmed with frugivorous, nectarivorous, insectivorous and sanguivorous guilds represented. Estimates using extrapolation place the real understory diversity somewhere above 30 species, making this a key site for conservation of bats in general, and the genera Sturnira, Platyrrhinus, and Vampyressa, in particular.
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Chiroptera Neotropical, 5(1-2), 1999
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the bats captured were understory phyllostomids, with
few exceptions. Nonetheless, high ecological diversity
was confirmed with frugivorous, nectarivorous,
insectivorous and sanguivorous guilds represented.
Estimates using extrapolation place the real understory
diversity somewhere above 30 species, making this a
key site for conservation of bats in general, and the
genera Sturnira, Platyrrhinus, and Vampyressa, in
particular.
INTRODUCTION
Studies in New World tropics are only now beginning
to assess the true diversity of Neotropical bats, but
sampling has been confined to a handful of well-
documented sites where research stations happen to
be located (Voss & Emmons 1996, Simmons & Voss
1998). This approach has left unexamined vast areas of
Neotropical forests, for which there are very few
comprehensive mammalian inventories. One such
critical information gap corresponds to the Colombian
Chocó (Voss & Emmons 1996). Based on its high
endemism and threats from human disturbance, the
Chocó tropical rainforest has been identified as a global
biodiversity hotspot (Olson & Dinerstein 1996).
Early mammal collections from the Pacific slopes of the
West Andes in Cauca list no bats for the nearby locality
of El Cocal, at 1200 m elevation (Allen 1916). Collections
by Kjell von Sneidern in the 1930s at five localities in
west Cauca left a gap in elevation between 900 and
1700 meters (Tamsitt and Valdivieso 1966). Modern bat
surveys in southwest Colombia have been spotty, with
only a handful of noteworthy records resulting in
publication (e.g., Alberico 1987, 1994). The picture that
emerges from these previous works is still fragmentary.
So far, the only sustained effort to inventory the middle
elevation bat faunas of the Chocó has taken place in
Nariño (south of Cauca, bordering Ecuador) at Reserva
Natural La Planada, 1,525 m elevation (Ospina-Ante &
Gómez 1995). Our survey lays the ground work for
future in-depth study of a montane bat fauna from the
middle elevations of the Pacific slopes of the West
Andes in Cauca, Colombia.
METHODS AND MATERIALS
Field Locality
Tambito Nature Reserve is located 50 km west of
Popayán on the Pacific slope of the Cordillera
Occidental, Cauca, Colombia, at 02°30’N 77°00’W. It is
adjacent to Parque Nacional Natural (PNN) Munchique,
and encompasses c. 3,000 ha. of very humid , both
premontane and lower montane forest, at 1,050–2,800
m. The yearly rainfall varies from 3,800mm to 7,000mm,
increasing with altitude. A seven-year rainfall record
from Tambito indicates a bimodal seasonality with
THE BAT FAUNA OF TAMBITO, COLOMBIA
Liliana M. Dávalos
Graduate Fellow - Department of Mammalogy,
American Museum of Natural History
Central Park West at 79th Street
New York, New York 10024-5192 USA
davalos@amnh.org
Jimmy A. Guerrero
Monitor de la Colección - Museo de Historia Natural,
Universidad del Cauca
Cra. 1ra No. 1A-27, Barrio Caldas
Popayán, Colombia
guerrero@ucauca.edu.co
ABSTRACT
This paper summarizes a first account of the bat fauna
in the middle elevations of the Tambito Nature Reserve
in the Colombian Chocó. A month-long survey using
mist netting found 13 genera comprising at least 26
species. As expected from mist net bias, virtually all
Chiroptera Neotropical, 5(1-2), 1999
Page 113
October/November and February/March being the
wettest months. The summer represents the dry season,
with high sensitivity to El Niño and La Niña. In 1997 (a
strong El Niño year), just 20mm of rain fell in the 3
months from June to September. Average temperatures
range from 13ºC to 19ºC depending on altitude. Relative
humidity is above 90% for much of the day (Jarvis &
Dávalos 1999).
The topography of Tambito is extremely complex. The
slopes are steep, being as high as 60 degrees in places,
with a great deal of spatial complexity on a small scale.
Epiphytic mosses characterize the physical appearance
of the forest in the upper reaches of the catchment and
in the more humid localities. Netting sites were selected
on the bases of accessibility from the cabin, diversity
of microhabitats, and striving to maintain sampling at
the same elevation, c. 1,500m.
METHODS
Ground-level (0-3 m) mist-netting and specimen
preparation followed standard methods described in
Simmons & Voss (1998) and Handley (1988)
respectively. Each captured bat was identified in the
field using Emmons (1997), Reid (1998), and Koopman
(1994). We also used unpublished dichotomous keys
for bats of the Chocó kindly facilitated by Drs. C.O.
Handley (Smithsonian Institution, Washington, D.C.)
and M.S. Alberico (Universidad del Valle, Cali).
Following Voss & Emmons (1996) vouchers of all
species encountered were preserved to document
identification. We collected liver tissue from each
specimen for DNA studies, prior to immersion in
formaldehyde. Conspicuous ectoparasites were also
collected. The specimen collection resulting from our
study was deposited at the Museo de Ciencias
Naturales, Universidad del Cauca (Popayán, Cauca).
Tissue samples and parasites were deposited at the
Molecular Laboratory of Instituto Alexander Von
Humboldt (Cali, Colombia).
RESULTS
In 24 nights of netting we captured 90 bats of 13 genera.
A definitive account, comprising at least 26 species
recorded is in progress (Dávalos & Guerrero in prep.).
All, except one (Myotis), of the 13 genera recorded
were Phyllostomids.
Taxonomic account
The preliminary taxonomic list resulting from our
sampling is summarized in Table 1.
Community ecology
A summary of relative capture abundance for different
diet-based guilds is presented in Table 2. As expected
from our sampling bias, most captured bats
(stenodermatines and carolliines) correspond to the
under-story frugivore guild. Size varies greatly among
the frugivores from large, e.g., Platyrrhinus, to medium,
e.g., Sturnira and Carollia, to small, e.g., Vampyressa.
Insectivores also show great size variation from tiny,
e.g. Myotis, to medium-large, e.g. Lonchorhina, but
size variation among nectarivores was almost null.
Genus Species (or number of species) Microhabitat
Desmodus rotundus Secondary
Phyllostomus 2Primary
Mimon crenulatum Edge
Lonchorhina aurita Secondary
Lonchophylla robusta Secondary, edge
Anoura 2Primary, secondary, edge
Carollia 2Primary, secondary
Sturnira 5Secondary, edge, stream
Platyrrhinus 3Primary, secondary, edge
Vampyressa 2Secondary, edge
Enchisthenes hartii Edge
Artibeus (Dermanura)2Primary, secondary
Myotis 3Secondary, edge
Table 1. Bats sampled at Tambito
Diet-based guild Number captures Percent captures
Frugivore 71 76.3%
Insectivore 11 12.0%
Nectarivore 88.6%
Sanguivore 11.1%
Table 2. Relative abundance in captures for different bat guilds
Chiroptera Neotropical, 5(1-2), 1999
Page 114
DISCUSSION
Pending definitive identification, the bat species
richness recorded at Tambito is relatively high, when
compared with sites of similar elevation in the Andes.
For the middle elevations of Nariño, 12 species have
been definitely recognized by Cadena et al. (1998), five
of which are also reported by Ospina-Ante & Gómez
(1995) in their species list that rises to 20. The results
of the latter, however, are inconclusive, as their
taxonomic account is still being revised (L.G. Gómez
pers. comm.).
Even with the limitations inherent to mist-net sampling
(Remsen & Good 1996), there was no sign of saturation
in capture for our survey (Figure 1) and the number
and range size of species suggests a rich and
ecologically diverse understory bat community.
Although estimation by extrapolation from capture data
is still in its infancy (Colwell & Coddington 1994), the
use of parametric and non-parametric estimators
indicate that real understory richness would be
somewhere between 30 and 45 species as seen in Figure
1.
Because mist netting was the only method used and it
is known to bypass most (if not all) aerial insectivores
(Simmons et al. 1998), the overall bat richness in
Tambito may be substantially higher. This, and the fact
that several Chocoan species of genera found in
Tambito (Sturnira, Platyrrhinus, Vampyressa) are
listed as near threatened or threatened by the IUCN
(IUCN 1996) confirm the reserve’s status as a key site
for the conservation of flying vertebrates (Donegan &
Dávalos 1999).
For conservation purposes, further bat inventories
using other methods e.g., ultrasound recording, will
allow more comprehensive study of the community,
especially since all modern surveys have used mist
netting protocols similar to our own. Additionally,
research in basic ecology and natural history of virtually
all the bats recorded is indispensable, as these basic
data are still unknown. There are, to our knowledge,
no published studies documenting specific foraging
behavior of bats in cloud forests of the Colombian
Chocó. Extensive work over several decades on Barro
Colorado Island, Panama, has shown fine-grain
partition of resources in the lowland bat community
(Kalko et al. 1996), similar efforts are necessary to
characterize rich chiropteran communities of higher
elevations.
ACKNOWLEDGEMENTS
Fieldwork for this survey was sponsored by the Royal
Geographic Society, Bat Conservation International,
the Institute for Latin American and Iberian Studies
and the Center for Environmental Research and
Conservation at Columbia University, and the
Figure 1. Parametric and non-parametric estimation by extrapolation from limited capture data. Observed captures
randomized 100 times are in black dots with error bars, adjusted Michaelis-Menten curve in black with maximum-
likelihood upper-boundary in squares, non-parametric estimators: jackknife and Chao’s in crosses and triangles,
respectively.
Chiroptera Neotropical, 5(1-2), 1999
Page 115
Explorers’ Club. Dr. Nancy B. Simmons provided
countless letters of recommendation and scientific
advice. Dr M. Mulligan and his HERB project at King’s
College London, the Museo de Historia Natural and
Fundación Proselva in Popayán facilitated logistics.
Many thanks to Q. Lame, Olga, L. González and A.
Bernal at the Tambito cabin. S. Reddy wrote the
programs for data analyses. This paper is dedicated to
the late A.J. Negret.
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(3) Glyphonycteris Thomas (including Barticonycteris Hill as a synonym), Micronycteris Gray (including Xenoctenes Miller as a synonym), and Trinycteris Sanborn are rediagnosed as distinct genera; Lampronycteris Sanborn and Neonycteris Sanborn, two other erstwhile subgenera of Micronycteris (sensu lato), should also be treated as full genera. (4) Micronycteris homezi Pirlot, based on a lost holotype and previously considered a nomen dubium, is redescribed and rediagnosed as a valid species. (5) Micronycteris megalotis (Gray) and M. microtis Miller are distinct species represented by sympatric collections from Paracou and other material similarly interpreted by recent investigators. (6) Mimon bennettii (Gray) and M. cozumelae Goldman are diagnosable as distinct species by consistent external and craniodental character differences. (7) Ectophylla H. Allen is rediagnosed to include Mesophylla Thomas in recognition of the sister-group relationship between E. alba H. Allen and E. macconnelli (Thomas). (8) The recent hypothesis that Sturnira lilium (E. Geoffroy) and 5. luisi Davis are conspecific is rejected as implausible because of trenchant cranial character differences. (9) The Venezuelan and French Guianan specimens recently identified in the literature as Eptesicus andinus J. A. Allen are not conspecific with the holotype of that species; instead, examination of type specimens, other comparative material, and the primary literature suggests that this material is referable to E. chiriquinus Thomas. (10) All currently accepted synonymies for taxa included within Davis's (1966) andinus group of Eptesicus are apparently incorrect; in our view, E. andinus is a senior synonym of E. montosus Thomas and E. chiralensis Anthony, whereas E. chiriquinus is a senior synonym of E. inca Thomas. (11) We review the contents of Cynomops Thomas, currently ranked as a subgenus of Molossops Peters, and tabulate diagnostic characters for the four species we regard as valid: M. abrasus (Temminck), M. greenhalli (Goodwin), M. paranus (Thomas), and M. planirostris (Peters). (12) Molossus barnesi Thomas is a valid species readily distinguishable from both M. molossus (Pallas) and M. coibensis J. A. Allen. Analyses of our sampling results indicate that (1) distinct sets of species are effectively sampled by different capture methods; (2) distinct sets of species inhabit different local habitats; and (3) increased sampling effort with any method generally results in more species, although the rate of accumulation declines with sample size (number of captures). Based on nonparametric statistical extrapolations, we estimate that the Paracou bat fauna probably consists of somewhere between 85 and 95 species; the more conservative richness estimator suggests that our inventory is perhaps about 90% complete. Judging from the known or inferred behaviors of the rare taxa (singletons and doubletons) in our data, most of the local species missing from this inventory are probably aerial insectivores, gleaning insectivores, or nectarivores. In terms of higher taxonomic composition, the bat fauna at Paracou is typical of those found throughout the humid Neotropical lowlands. A quantitative analysis of faunal similarity at the species level among 14 rainforest localities chosen as exemplars clusters the Paracou list with others previously reported from the Guiana subregion of Amazonia, next with lists from elsewhere in Amazonia, and lastly with Central American lists. Not surprisingly, pairwise similarity values show a positive correlation between faunal resemblance and geographic proximity within the Neotropical rainforest biome. Many (47%) of the bat species in the Paracou fauna are essentially pan-Neotropical in distribution and most of these are also known from habitats other than rainforest. The remaining species exhibit more restricted geographic distribution patterns, but true Amazonian endemics constitute only a minor fraction of the Paracou bat fauna. Species richness comparisons among inventory sites are complicated by problems of inconsistent methodology, habitat representation, and sampling effort. For example, the apparently exceptional diversity of emballonurids, phyllostomines, and molossids in the Paracou fauna is plausibly explained by our intensive use of elevated netting and roost surveys, and by prolonged effort, all of which factors act to reduce the well-known capture bias of ground-level mistnets (which consistently undersample these taxa in the short term). However, the low richness of carolliines and stenodermatines at Paracou by comparison with most other Amazonian (especially western Amazonian) localities is apparently real. The only approximately valid statistical comparison of species richness that we can make between sites based on published capture-frequency data suggests an increase of approximately 50% in understory bats from eastern Central America to Amazonia, but the real or artifactual nature of this estimated difference remains to be evaluated. A trophic classification of Paracou bats indicates that aerial insectivores are the most speciose feeding guild in the local fauna, followed by gleaning animalivores, frugivores, and nectarivores; ominivores, sanguivores, and piscivores are minor components. Patterns of differential habitat use among species within some feeding guilds can be inferred from our capture-frequency data, notably for aerial insectivores and frugivores. By contrast, gleaning animalivores appear to be largely restricted to primary forest, a puzzling phenomenon previously reported from other Neotropical rainforest localities. To facilitate future inventory fieldwork we provide (1) detailed descriptions of survey and capture methods, (2) illustrations of most local habitats recognized as distinct, (3) complete breakdowns of capture frequencies by method and habitat for each species, (4) photographs of numerous roosts at which bats were captured, and (5) descriptions and/or illustrations of useful characters for identifying species hitherto frequently confused in the field. Finally, we make recommendations for improving bat inventory efficiency, suggest minimal standards for reporting inventory data, urge the adoption of quantitative methods for intersite diversity comparisons, and comment on the prospects for rapid diversity assessment of rainforest bat faunas.
Article
Information about the magnitude and geographic distribution of mammalian diversity in Neotropical lowland rainforests is important for evaluating research and conservation priorities in Central and South America. Although relevant inventory data are rapidly accumulating in the literature, real site-to-site diversity differences are hard to identify because many confounding factors can affect the size and composition of faunal lists. Herein we assess the available information about Neotropical rainforest mammal diversity and suggest guidelines for future work by reviewing inventory methods, documenting and discussing faunal lists from ten localities, and summarizing geographic range data to predict diversity patterns that can be tested by field and museum research. All inventory methods are biased because each is suitable for collecting or observing only a fraction of the morphologically and behaviorally diverse mammalian fauna that inhabits Neotropical rainforests. Hence, many methods must be used in combination to census whole communities. Although no combination of methods can be guaranteed to produce complete inventories, the omission or nonintensive application of any of several essential methods probably guarantees incomplete results. We recommend nine methods that, used intensively and in combination, should maximize the efficiency of future inventory fieldwork. Ten rainforest mammal inventories selected as exemplars illustrate several common problems: sampling effort is highly variable from study to study, species accumulation curves are not asymptotic for any fauna, essential field methods were omitted in every case, and some localities were partially defaunated by hunters prior to inventory. Meaningful diversity comparisons are therefore impossible without a major investment in additional fieldwork at each site. Geographic range data provide an essential alternative source of diversity estimates. Comparisons of inventory results with geographic expectations (diversity predictions based on range data) suggest that all existing inventories are incomplete, that the degree of incompleteness is inversely correlated with inventory duration, and that special methods are required to add elusive species to faunal lists. The range data at hand also suggest several geographic patterns that should be tested with carefully focussed fieldwork. (1) Mammalian diversity in Amazonia is probably greatest in the western subregion (between the Rio Negro and the Rio Madeira, where over 200 species might be sympatric at some localities), least in the Guiana subregion (east of the Negro and north of the Amazon), and intermediate in southeastern Amazonia (east of the Madeira and south of the Amazon). (2) Geographic variation in Amazonian diversity chiefly involves marsupials, bats, primates, and rodents; by contrast, xenarthran, carnivore, and ungulate faunas are remarkably uniform across the entire region. (3) In Central American rainforests, a conspicuous and apparently monotonic diversity gradient extends from eastern Panama (where mammalian diversity is within the range of Amazonian values) to southern Mexico (where mammalian diversity may be less than anywhere else on the rainforested Neotropical mainland). Mammalian diversity in coastal Venezuelan and southeastern Brazilian rainforests is difficult to assess with existing literature and collection resources, but neither region is likely to be as diverse as Amazonia. Despite a few dissenting voices, the literature of New World mammalogy provides compelling evidence that mammalian diversity, as measured by sympatric species richness, is greatest in lowland tropical rainforests and decreases along gradients of increasing latitude, elevation, and aridity. Thus, the mammalian faunas of western Amazonia are the most diverse of any in the Americas and perhaps in the world. We briefly discuss the generality and causes of observed diversity patterns in terms of contemporary ecology and historical scenarios. Significant advances in understanding mammalian diversity patterns in Neotropical rainforests will require systematic revisions of many problematic genera and an aggressive program to inventory poorly sampled areas while opportunities to do so yet remain.
Chapter
The study of processes that influence the distribution, diversity, and abundance of species is one of the most challenging and complex fields in biology. Many basic questions are still controversial. As the results of an increasing number of studies clearly demonstrate, good data on temporal and spatial variability in community composition and species abundance are essential for formulating and evaluating hypotheses about the processes determining organization of communities and diversity of species. However, recent studies indicate that ecomorphologically similar species may be clearly differentiated by behavioral traits such as spatial segregation in habitat use, roost site selection, foraging strategies, and diet. Ecomorphological predictions alone would have placed these species closer together in the community than they actually are. Furthermore, relative abundance of well-sampled species showed individual year-to-year variation. Some frugivorous species with large seasonal variation in numbers may be migratory, but except for one species that declined, long-term population trends remained rather constant. Long-term monitoring of bats at many localities is urgently needed to build databases for intercommunity comparisons.
Article
Both the magnitude and the urgency of the task of assessing global biodiversity require that we make the most of what we know through the use of estimation and extrapolation. Likewise, future biodiversity inventories need to be designed around the use of effective sampling and estimation procedures, especially for `hyperdiverse' groups of terrestrial organisms, such as arthropods, nematodes, fungi, and microorganisms. The challenge of estimating patterns of species richness from samples can be separated into (i) the problem of estimating local species richness, and (ii) the problem of estimating the distinctness, or complementarity, of species assemblages. These concepts apply on a wide range of spatial, temporal, and functional scales. Local richness can be estimated by extrapolating species accumulation curves, fitting parametric distributions of relative abundance, or using non-parametric techniques based on the distribution of individuals among species or of species among samples. We present several of these methods and examine their effectiveness for an example data set. We present a simple measure of complementarity, with some biogeographic examples, and outline the difficult problem of estimating complementarity from samples. Finally, we discuss the importance of using `reference' sites (or sub-sites) to assess the true richness and composition of species assemblages, to measure ecologically significant ratios between unrelated taxa, to measure taxon/sub-taxon (hier-archical) ratios, and to `calibrate' standardized sampling methods. This information can then be applied to the rapid, approximate assessment of species richness and faunal or floral composition at `comparative' sites.