Wildlife Movements and Landscape Connectivity in the Tarangire Ecosystem

Lohay, George G.; Riggio, Jason; Lobora, Alex; Kissui, Bernard M.; Morrison, Thomas A.

doi:10.1007/978-3-030-93604-4_12

Cited by 6 publications

(6 citation statements)

References 69 publications

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“…Similar to Lake Manyara, population densities of resident large herbivores in the Mto wa Mbu GCA, where there are limited anti-poaching measures, are very small (giraffe), functionally absent (elephant), and generally well below historical baselines 35 . Nevertheless, wildlife still occurs in this area and the landscape seems to be permeable for wildlife, especially for wildebeest and zebra which use this area for their annual migration to the Northern Plains 28 , even though agricultural and infrastructural development threaten this functional connectivity in several locations 49 .…”

Section: Discussionmentioning

confidence: 99%

The contribution of community-based conservation models to conserving large herbivore populations

Kiffner,

Foley,

Lee

et al. 2024

Sci Rep

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In East Africa, community-based conservation models (CBCMs) have been established to support the conservation of wildlife in fragmented landscapes like the Tarangire Ecosystem, Tanzania. To assess how different management approaches maintained large herbivore populations, we conducted line distance surveys and estimated seasonal densities of elephant, giraffe, zebra, and wildebeest in six management units, including three CBCMs, two national parks (positive controls), and one area with little conservation interventions (negative control). Using a Monte-Carlo approach to propagate uncertainties from the density estimates and trend analysis, we analyzed the resulting time series (2011–2019). Densities of the target species were consistently low in the site with little conservation interventions. In contrast, densities of zebra and wildebeest in CBCMs were similar to national parks, providing evidence that CBCMs contributed to the stabilization of these migratory populations in the central part of the ecosystem. CBCMs also supported giraffe and elephant densities similar to those found in national parks. In contrast, the functional connectivity of Lake Manyara National Park has not been augmented by CBCMs. Our analysis suggests that CBCMs can effectively conserve large herbivores, and that maintaining connectivity through CBCMs should be prioritized.

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Section: Discussionmentioning

confidence: 99%

The contribution of community-based conservation models to conserving large herbivore populations

Kiffner,

Foley,

Lee

et al. 2024

Sci Rep

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“…The two largest giraffe populations in the Tarangire Ecosystem are located in the TNP and MRC (Lee & Bolger, 2017 ) whose boundaries are only 4 km apart. In the past the TNP‐MRC‐Lake Natron wildlife corridor provided connectivity between MRC and TNP, but this corridor has seen a recent dramatic increase in agriculture and human populations potentially reducing wildlife dispersal (Jones et al, 2009 ; Kikoti, 2009 ; Lohay et al, 2022 ; Msoffe et al, 2011 ). This corridor is bisected by a major tarmac highway (A104) that wildlife must cross to move between TNP and MRC and much of the expansion of human activities in the Tarangire Ecosystem has occurred along this road.…”

Section: Discussionmentioning

confidence: 99%

“…The Serengeti Ecosystem (~33,000 km 2 ) and the Tarangire Ecosystem (~25,000 km 2 ) are two of the most critical ecosystems in Tanzania for biodiversity conservation. Both ecosystems conserve biodiversity and large landscapes, and support two of Africa's few remaining long-distance migrations of large mammals including the white-bearded wildebeests (Connochaetes taurinus) and the plains zebras (Equus quagga) and along with their major predators including lions (Panthera leo) and leopards (Panthera pardus) (Bond et al, 2022;Estes, 2014;Guy et al, 1981;Hopcraft et al, 2013;Lamprey, 1964;Lohay et al, 2022;Morrison et al, 2016;Prins & de Jong, 2022;Sinclair, 2012). Each ecosystem also host two of the largest remaining populations of Masai giraffes (Figure 1b), (Bolger et al, 2019;Lee & Bolger, 2017; Lee & Bond, 2022; Lee & Strauss, 2016;Strauss et al, 2015), with substantial contributions to vegetation dynamics, food webs, and community ecology.…”

Section: Introductionmentioning

confidence: 99%

Genetic evidence of population subdivision among Masai giraffes separated by the Gregory Rift Valley in Tanzania

Lohay

Lee

Wu-Cavener

et al. 2023

Ecology and Evolution

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The Masai giraffe has experienced a population decline from 70,000 to 35,000 in the past three decades and was declared an endangered subspecies by the IUCN in 2019. The remaining number of Masai giraffe are geographically separated by the steep cliffs of the Gregory Rift escarpments (GRE) in Tanzania and Kenya dividing them into two populations, one west and one east of the GRE. The cliffs of the GRE are formidable barriers to east–west dispersal and gene flow and the few remaining natural corridors through the GRE are occupied by human settlements. To assess the impact of the GRE on Masai giraffe gene flow, we examined whole genome sequences of nuclear and mitochondrial DNA (mtDNA) variation in populations located east (Tarangire ecosystem) and west (Serengeti ecosystem) of the GRE in northern Tanzania. Evidence from mtDNA variation, which measures female‐mediated gene flow, suggests that females have not migrated across the GRE between populations in the Serengeti and Tarangire ecosystems in the past ~289,000 years. The analysis of nuclear DNA variation compared to mtDNA DNA variation suggests that male‐mediated gene flow across the GRE has occurred more recently but stopped a few thousand years ago. Our findings show that Masai giraffes are split into two populations and fulfill the criteria for designation as distinct evolutionary significant units (ESUs), which we denote as western Masai giraffe and eastern Masai giraffe. While establishing giraffe dispersal corridors across the GRE is impractical, conservation efforts should be focused on maintaining connectivity among populations within each of these two populations. The importance of these efforts is heightened by our finding that the inbreeding coefficients are high in some of these Masai giraffe populations, which could result in inbreeding depression in the small and fragmented populations.

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“…Our results illustrating the importance of law enforcement echo the findings of both a study of West African giraffes (G. c. peralta ) in Niger, which showed remarkably high population growth rates after strong law enforcement efforts drastically reduced poaching (Suraud et al, 2012), as well as a population viability analysis conducted for a small population of Kordofan giraffes ( G. c. antiquorum ) in Cameroon (Colston et al, 2023). If effective wildlife law enforcement were to be expanded to village lands outside of our IBM study area, legal livelihoods were promoted, and wildlife movement pathways were permanently protected to enable giraffes as well as migratory ungulates to access high‐quality habitats (Bond et al, 2017; Lee & Bolger, 2017; Lohay et al, 2022), these measures would very likely increase the metapopulation of Masai giraffes in the greater Tarangire Ecosystem and contribute toward the recovery of this endangered (sub)species (Bolger et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

Extinction risks and mitigation for a megaherbivore, the giraffe, in a human‐influenced landscape under climate change

Bond,

Lee,

Paniw

2023

Global Change Biology

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Megaherbivores play “outsized” roles in ecosystem functioning but are vulnerable to human impacts such as overhunting, land‐use changes, and climate extremes. However, such impacts—and combinations of these impacts—on population dynamics are rarely examined using empirical data. To guide effective conservation actions under increasing global‐change pressures, we developed a socially structured individual‐based model (IBM) using long‐term demographic data from female giraffes (Giraffa camelopardalis) in a human‐influenced landscape in northern Tanzania, the Tarangire Ecosystem. This unfenced system includes savanna habitats with a wide gradient of anthropogenic pressures, from national parks, a wildlife ranch and community conservation areas, to unprotected village lands. We then simulated and projected over 50 years how realistic environmental and land‐use management changes might affect this metapopulation of female giraffes. Scenarios included: (1) anthropogenic land‐use changes including roads and agricultural/urban expansion; (2) reduction or improvement in wildlife law enforcement measures; (3) changes in populations of natural predators and migratory alternative prey; and (4) increases in rainfall as predicted for East Africa. The factor causing the greatest risk of rapid declines in female giraffe abundance in our simulations was a reduction in law enforcement leading to more poaching. Other threats decreased abundances of giraffes, but improving law enforcement in both of the study area's protected areas mitigated these impacts: a 0.01 increase in giraffe survival probability from improved law enforcement mitigated a 25% rise in heavy rainfall events by increasing abundance 19%, and mitigated the expansion of towns and blockage of dispersal movements by increasing abundance 22%. Our IBM enabled us to further quantify fine‐scale abundance changes among female giraffe social communities, revealing potential source–sink interactions within the metapopulation. This flexible methodology can be adapted to test additional ecological questions in this landscape, or to model populations of giraffes or other species in different ecosystems.

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Wildlife Movements and Landscape Connectivity in the Tarangire Ecosystem

Cited by 6 publications

References 69 publications

The contribution of community-based conservation models to conserving large herbivore populations

The contribution of community-based conservation models to conserving large herbivore populations

Genetic evidence of population subdivision among Masai giraffes separated by the Gregory Rift Valley in Tanzania

Extinction risks and mitigation for a megaherbivore, the giraffe, in a human‐influenced landscape under climate change

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