It is widely accepted that tropical lowland forests are ...



69EG3291 Third Year Project

The Influences of Amazonian Landscape

Heterogeneity on the Distribution of a

Terrestrial Mammal Assemblage

at Las Piedras Biodiversity Station,

Southeast Peru.

J. McCauley

A project submitted in partial fulfilment of the requirements for the degree of Bachelor of Science (Honours) in Geography, The Manchester Metropolitan University.

Department of Environmental and Geographical Sciences

The Manchester Metropolitan University

April 2008

1.0 INTRODUCTION

Tropical lowland forests are the most species-rich terrestrial ecosystem (Vanclay, 1991; DeVries and Walla, 2001; Bush and Lovejoy, 2007). Various anthropogenic processes such as logging and habitat conversion have exacerbated the global crisis concerning this environment (Dumbrell and Hill, 2005). Currently, there is a strong emphasis on the cultural and economic sustainability of long-term conservation strategies, involving fresh and imaginative approaches to tropical ecology, rather than intrusive, polarised, non-collaborative conservational attitudes that have besieged tropical wildlands over several decades (DeFries et al., 2005; Lamb et al., 2005; Vaughan, 2000).

The Neotropic ecozone contains the most species-diverse tropical forests on the planet, the biggest of which is the Amazon rainforest, encompassing approximately 6 x 106 km2 and spanning eight countries (Gentry, 1988; Waterloo et al., 2006; Muller-Karger et al., 1988). It occupies the world’s largest river basin, comprising of over half of the world’s tropical forests and containing one third of the world’s species (Kimerling, 2001; McNeely et al., 1990). Tropical mammals are often charismatic animals that hold public attention with their extraordinary characteristics and behaviours (Eisenberg and Redford, 1999). The Peruvian Amazonian region accommodates particularly high levels of diversity and accomodates one of the richest and most diverse tropical mammalian communities in the world (McNeely et al., 1990; Pogue, 1996).

1.1 Importance of faunal censuses

Habitat loss and fragmentation is the main cause of the decline in biodiversity in tropical forests, therefore, strategies for conservation in the areas affected are of relatively high importance (Hill and Curran, 2005; Uehara-Prado et al., 2007). There is constant lobbying for more protection in the Amazon, aimed to prevent a cascading breakdown of the Amazon’s ecosystem, through preventative management of the environment (Fearnside, 2001; Peres and Lake, 2001).

Recording the species make up can be an essential tool in supporting proposals for national parks and reserves (Andelman and Fagan, 2000). A faunal census that confirms the presence of a charismatic species such as Jaguar Panthera onca or Tapir Tapiridae spp. will undoubtedly aid proposals for conservation (Sergio et al., 2006).

Given the current rate at which biodiversity is declining, conservation organisations constantly face the problem of precisely where and how to direct their resources, in the endeavour to protect the organisms of greatest conservational, ecological or environmental value (Wilson et al., 2006). This requires the prioritisation of targets, which are identified at varying scales. It may therefore prove highly worthwhile to investigate areas that have the potential to contain valuable communities but are deficient of scientific substantiation.

1.2 Keystone concept

An important theme amongst conservation biologists is to identify and conserve keystone species: A species with a disproportionately small physical existence compared to the overall ecological influence that it exerts on its environment. Following Paine’s (1969) introduction of the keystone species concept, it has been an influential device for biodiversity management. In recent times, uncertainties about the definition (Piraino and Fanelli, 1999) and issues regarding the accuracy of the concept have lead to new approaches to define valuable entities within an ecosystem (Andelman and Fagan, 2000; Caro and O’Doherty, 1999; Paine, 1995; Power et al., 1996).

Tews et al., (2004) suggested a modified concept inspired by the keystone species concept, which also acknowledges the importance of subjects other than a species that is a crucial structure, and may have a significant influence upon the surrounding biological environment. This theory makes allowances for the fact that the term ‘keystone species’ is often too specific, because other species with the relevant characteristics share its role or could occupy the same ecological niche. It also accounts for the fact that many inert entities are essential components of ecosystems such as temporary water bodies and salt licks.

In the conclusion of Tews et al., (2004), it was advised that studies testing the keystone structure concept in the field could be considerably beneficial for nature conservation and biodiversity management. This paper presents an analysis of the relationships between habitat characteristics and mammal diversity and species composition in the Peruvian Amazon, derived from primary data collected in the field. Multivariate cluster analysis is used to obtain irregularities allowing the detection of potential keystone structures. The results are assessed using the local natural history of the species and biological trends found in other tropical environments.

1.3 Selection of study area

Protection of rare and ecologically valuable species and associated habitats requires management decisions to ensure that viable populations are maintained (Possingham et al., 2001). This management must be based on robust ecological acumen, which is absent for mammals in parts of southeast Peru.

Despite their small physical substance within a rainforest, Mammals play an important role within the ecosystem through various activities such as consumption and seed dispersal (Christianini and Galetti, 2007). Many mammal abundance investigations have been carried out across Amazonia (e.g. Eisenberg and Thorington, 1973; Eisenberg, 1979; Emmons, 1995; Glanz, 1982; Janson and Emmons 1990; Parry et al., 2007; Mendes-Pontes, 2004; Trolle, 2003) however there are still many areas that have received little scientific discourse.

The Las Piedras River in the department of Madre de Dios, Peru, has received little attention with regard to abundance, species make-up and habitat-relationships in the mammal community. Tatum-Hume et al., (2006) is the only publication that has endeavoured to portray the species make-up of terrestrial mammals with censuses along the Las Piedras River.

Much of the Las Piedras River has undergone selective logging, especially in the immediate vicinity of the river. The data for this experiment was collected at a relatively undisturbed site, the terrestrial mammalian community in the area is reported to be relatively comprehensive (Tatum-Hume et al., 2006), there was however a marked absence of economically valuable hardwood tree species such as mahogany.

The most popular methods of faunal assessment available to ecologists include live-trapping, camera trapping, line-transect walks and track-trapping. The most appropriate method for this study was track-trapping; the only method that is ethical, inexpensive, and has the potential to detect elusive mammals.

The track-trapping method has been used effectively worldwide, in a variety of environments (Dice, 1941; Scattergood, 1954; Smallwood and Fitzhugh, 1995). It’s effectiveness on tropical forest trails has been also highlighted by studies (Carrillo et al., 2000; Mandujano and Gallina 1995).

This paper describes results of track trapping sites, which were monitored over a 15-day period from July 1st 2007, coupled with habitat surveys through which the characteristics and contents of 84 plots were recorded. The presence of species from the four largest terrestrial-mammalian orders were detected; Perissodactyla, Artiodactyla, Rodentia and Carnivora.

The primary aim of this paper is to provide a contemporary portrayal of the terrestrial mammal community at Las Piedras. Moreover, this paper presents conservational recommendations by highlighting important keystones within the ecosystem, and considerations that may be useful for future track-trap and habitat surveys in tropical forests. The objectives of this investigation are, (1), measure a variety of potential keystone structures in the field, (2), record the presence or absence of terrestrial mammal tracks at each plot, (3), statistically analyse the data for significant correlations which may reveal keystone structures.

2.0 STUDY AREA

2.1 Habitat terminology

Forests that are not seasonally inundated (hereafter, terra firme) make up 91% of the Amazon basin, and are generally characterised by relatively dry, well-drained forest floors, and soils that lack nutrients (Haugaasen and Peres, 2005a). Seasonally inundated forests (hereafter, floodplain) make up less than 2% of the Amazon basin, and are defined as those that are heavily affected by dynamic fluvial regimes, which cause large environmental disturbances and deposit alluvial sediments that alter the forest structure (Nebel et al., 2001; Peres, 1997).

2.2 Sampling sites

The study area (Figure 1) is located in the department of Madre de Dios, southeast Peru (12° 3'24.07"S, 69°31'43.04"W). Elevation is below 500m, with a humid tropical climate and dry period that is usually between July and November (Lee et al., 2005), during which the mean temperature is 23.5ºC and mean monthly rainfall is ................
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