Diversity and habitat use of medium-large sized mammals across oil palm landscapes in the Llanos region of Colombia

Pardo Vargas, Lain Efrén (2018) Diversity and habitat use of medium-large sized mammals across oil palm landscapes in the Llanos region of Colombia. PhD thesis, James Cook University.

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View at Publisher Website: https://doi.org/10.25903/5be8adb35232e
 
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Abstract

Rising demand for products derived from oil palm has resulted in accelerated expansion of its global cropping area. In Southeast Asia, where most of world's oil palm is produced, forest loss due to oil palm cultivation has become one of the major threats to biodiversity. As reviewed in Chapter 1, oil palm is now rapidly expanding in Latin America, where Colombia is the largest oil palm producer with nearly 500,000 ha currently under cultivation. Although most oil palm expansion in Colombia has taken place on partially degraded lands or in areas previously used for crops or livestock, little is known about the biodiversity that currently exists in these landscapes and the effect that expanded oil palm agriculture will have. Because Colombia is one of the world's most biodiverse countries, understanding how oil palm production affects wildlife communities is vital to inform conservation planning and improve land-management practices.

In this thesis, I used mammal species as a focal group to evaluate how fauna have responded to expanding oil palm production in Colombia. Mammals are a diverse group and, as such, are good indicators of ecosystem degradation. This is because mammals occupy a wide range of ecological niches, have important and varied roles at a range of different trophic levels, and are often vulnerable to habitat fragmentation.

I conducted this study in the rural areas surrounding the towns of Restrepo, Cumaral, Cabuyaro, Acacias, Castilla la Nueva, and San Carlos de Guaroa, in the Department of Meta, in the eastern plains or Llanos Orientales region of Colombia. This region, which has become the largest oil palm-production zone in the country, is a seminatural savanna ecosystem interspersed by riparian forests of differing sizes and ages along rivers and streams and human land uses such as grazing and agriculture. Within this study area, I used unbaited, automatic camera traps at 56 sites located each at least 2 km apart (33 sites in oil palm plantations and 23 in riparian forest), spanning a total area of ~2,000 km² (194‒394 m.a.s.l.) to detect terrestrial medium- and large-sized mammals (>0.5 kg). In the Llanos region, knowledge of the ecology and distribution of most terrestrial mammals is very limited. Therefore, I used multiple approaches (as described below) to address these gaps and understand the responses of mammals to oil palm plantations and other local- and landscapelevel environmental factors in the Colombian Llanos.

First, in Chapter 2, I examined how species richness, abundance and composition of terrestrial mammal species differed between oil palm plantations and riparian forests. I also determined the influence of landscape- and habitat-level features on those metrics. Data from 12,403 camera-days revealed that species richness and the community-level composition of mammals differed significantly between oil palm and riparian forest, with site-level richness in oil palm plantations being 47% lower, on average, than in riparian forests. Within plantations, mammalian species richness was strongly and negatively correlated with the abundance of cattle, and positively correlated with the density of undergrowth vegetation.

Across the study area, the community composition of mammals at each camera-trap site was significantly influenced by cover type (oil palm versus riparian forest), the percentage of forest remaining, and the distance to the nearest town. Within oil palm sites, understory vegetation, cattle abundance, and canopy cover had significant effects on community composition. Species-specific responses varied between habitat types, with oil palm having positive effects on the abundance of medium-sized omnivore/carnivores, insectivores and grazers such as jaguarundi (Puma yagouaroundi), fox (Cerdocyon thous), giant anteater (Myrmecophaga tridactyla) and white-tailed deer (Odocoileus cariacou). My findings suggest that increasing habitat complexity and retaining native riparian forest – regardless of its physiognomic structure – in oil palm-dominated landscapes will help to support higher native mammal richness and abundance at both local and landscape scales.

Second, building on the above findings and in preparation for the imminent expansion of oil palm production in Colombia, I aimed to identify critical transition points (thresholds) in land cover change at which mammal communities drastically change. Identifying thresholds is especially crucial to anticipate sustainable oil palm-cover limits for conservation planning. Therefore, in Chapter 3, I investigated the possible existence of change points for terrestrial mammal richness and community composition along an increasing gradient of oil palm cover in the study area, which covered approximately 2,000 km². At each camera-trap site, I found a negative linear relationship between the proportion of oil palm and species richness, but no evidence for significant threshold effects on richness per se. In contrast, I found strong signs of a threshold change in mammal community composition when oil palm cover in the zone immediately surrounding the camera-trap reached 45-75%, beyond which mammalian species community composition drastically changed. Moreover, when species were assessed individually, a significant threshold response to oil palm land cover was found to occur in 10 of 15 species, with four [squirrel (Sciurus spp), agouti (Dasyprocta fuliginosa), spiny rat (Proechimis spp), common opossum (Didelphis marsupialis)] having a negative threshold at approximately 45% oil palm cover. The other five species showed no evidence of any critical transition point [giant anteater, lesser anteater (Tamandua tetradactyla), jaguarondi, white-tailed deer and crap-eating raccoon (Procyon cancrivorus)].

These findings contribute to the identification of the maximum oil palm cover allowable within production zones in Colombia to ensure the conservation of terrestrial mammals. I then used the 45-75% oil palm-cover threshold I identified to examine the conservation status of oil palm production zones across all of Colombia (North, South, West and East zones). For this assessment, I first delimited the spatial extend of each of these zones using the farthest plantations as the limit, as there is no official delimitation for each zone. Then, I used the community threshold identified above as a baseline and determined the percentage of oil palm at each production zone relative to that threshold in relation to the extent of these zones within a fishnet composed of 1 km² squares, constructed to cover the size of each production zone. I found that 41% of the ~340,000 ha total area covered by these four zones had already crossed the 45-75% threshold. This result suggests a need for urgent restoration of native forest to increase its extent in these zones if a potential collapse of mammal communities is to be avoided. The identified threshold for oil palm coverage can be used as a guideline to anticipate the minimum amount of remaining native forest needed to support resilient populations of mammals. As such, my results also suggest that maintaining a minimum forest cover of 25-55% in Llanos oil palm-dominated landscapes will help to promote mammal conservation—avoiding a 'risk zone' of drastic population declines.

Third, while the positive conservation role of remaining natural habitats in anthropogenic landscapes is relatively clear, quantifying the degree to which the agricultural matrix imposes limitations on animal use and movements is vital to understand species' resilience to land-use change. In Chapter 4, I evaluated the habitat use and detection probabilities of 23 medium- and large-sized mammals in oil palm plantations and adjacent riparian forest in the Llanos region, using an occupancy framework. I also assessed the effect of undergrowth vegetation and proximity to forest on habitat-use probability within oil palm sites. Most species were detected only rarely, limiting the analysis to the 12 most common species found in both habitat types. This issue was particularly evident in oil palm, because seven species found in riparian forests were never detected there. Habitat use (Ψ^) was strongly influenced by habitat type for four species, showing a strong negative effect of oil palm, whereas the remaining eight species showed no effect of habitat type.

As expected, probabilities of oil palm and forest use varied somewhat among species. In general, omnivorous mesocarnivores, white-tailed deer, and the giant anteater were more likely to use oil palm whereas the remaining species, including ocelot (Leopardus pardalis) and lesser anteaters, showed a preference for forest habitats. In general, my findings suggest that retaining undergrowth vegetation inside plantations and maintaining nearby riparian corridors will reduce the negative impacts that a homogenous monoculture, such as an oil palm plantation, exerts on native mammal species. One caveat of this study is that historical land uses have varied across the Llanos region, potentially complicating the patterns I detected.

The ability of some animal species to adjust their behaviour in response to landscape changes and human presence may allow them to better adapt to new, human-altered conditions. However, behavioral responses to land-use change by mammal species are not well documented. In Chapter 5, I quantified the activity patterns of several terrestrial mammal species to investigate how this aspect of animal behaviour differs between oil palm plantations and riparian forests. I also evaluated the effect of human activity on the activity patterns of mammal species and examined temporal overlap of activity between species to investigate potential species interactions. I used 2,515 camera trap records of 23 mammal species from 12,403 camera days, and analyzed the data using Kernel density estimation and the coefficient of temporal overlap (Δ). Data were sufficient to assess the activity patterns of 10 species in riparian forest and seven species in oil palm plantations. Of these, four species [capybara (Hydrochaerus hydrochaeris), giant anteater, lesser anteater and common opossum] were represented by enough records (n > 20) in both oil palm and forest to allow for robust comparisons. Only capybaras showed a shift in activity patterns, changing from being crepuscular in the forest to predominantly nocturnal in oil palm plantations. Regarding the effect of humans on the activity patterns of mammals, capybaras, giant anteaters and white-tailed deer appeared to modify their activities to avoid human activities in oil palm plantations by becoming more crepuscular or nocturnal. This was not true of jaguarondi, which displayed activity levels that strongly overlapped temporally with human activities.

Pair-wise analyses suggested that temporal segregation occurred between some species occupying the same trophic position (e.g. fox and jaguarundi) within oil palm plantations, whereas conversely some predators and their prey (e.g. ocelot and armadillo [Dasypus novemcinctus]) had high overlaps in temporal activity patterns in riparian forest. My findings shed light on how the conversion of native forest to oil palm plantation can lead to behavioral changes of wildlife, a feature of the effect of anthropogenic land use change that is not frequently assessed.

This thesis is the most comprehensive analysis to date examining the effects of oil palm plantations on Colombian terrestrial mammals. Overall, my findings help document mammal diversity in oil palm-dominated landscapes in Colombia and improve understanding of the complex ecological relationships among mammal species in these landscapes. Importantly, oil palm plantations were unsuitable habitat for most native species. The environmental conditions and the history of oil palm development in the Colombian Llanos is dissimilar to that of Southeast Asia. Therefore, we cannot rely on information and recommendations from studies in that region to evaluate the South American context. We must consider the geographical and environmental particularities and land-use history of each geographic area when evaluating impacts of oil palm production on Colombia's biodiversity. As such, the conclusions and recommendations contained in this thesis provide valuable information from which to develop more effective management practices to retain native mammals in Colombian oil palm landscapes.

Item ID: 56106
Item Type: Thesis (PhD)
Keywords: African palm, agriculture, agroecosystem, anteaters, camera trap, carnivores, circadian rhythms, deforestation, diel activity, gallery forest, human dominated landscape, land-use change, Llanos Orientales, Llanos, matrix resistant, mesopredators, Neotropics, occupancy, oil palm, Orinoquia, palm oil, permeability, policy, richness, riparian forest, riparian, RSPO, savanna, survey design, temporal segregation, tipping point, TITAN analysis, transect
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Copyright Information: Copyright © 2018 Lain Efrén Pardo Vargas
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 1: Pardo Vargas, Lain Efrén, Laurance, William F., Clements, Gopalasamy Reuben, and Edwards, Will (2015) The impacts of oil palm agriculture on Colombia's biodiversity: what we know and still need to know. Tropical Conservation Science, 8 (3). pp. 828-845.

Chapter 2: Pardo, Lain E., Campbell, Mason J., Edwards, Will, Clements, Gopalasamy Reuben, and Laurance, William F. (2018) Terrestrial mammal responses to oil palm dominated landscapes in Colombia. PLoS ONE, 13 (5).

Chapter 3: Pardo Vargas, Lain E., de Oliveira Roque, Fabio, Campbell, Mason J., Younes, Nicolas, Edwards, Will, and Laurance, William F. (2018) Identifying critical limits in oil palm cover for the conservation of terrestrial mammals in Colombia. Biological Conservation, 227. pp. 65-73.

Chapter 6: Pardo, Lain E., Clements, Gopalasamy Reuben, Edwards, Will, Rojas-Rojas, Angela V., and Laurance, William F. (2017) Registros de puma (Puma concolor Linnaeus, 1771) en zona rural de San Carlos de Guaroa, Meta, Colombia / Records of cougar (Puma concolor, Linnaeus, 1771) in the countryside of San Carlos de Guaroa, Meta, Colombia. Revista Biodiversidad Neotropical, 7 (2). pp. 104-109.

Date Deposited: 11 Nov 2018 22:56
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960899 Flora, Fauna and Biodiversity of Environments not elsewhere classified @ 100%
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