Extinctions, genetic erosion and conservation options for the black rhinoceros (Diceros bicornis)

The black rhinoceros is again on the verge of extinction due to unsustainable poaching in its native range. Despite a wide historic distribution, the black rhinoceros was traditionally thought of as depauperate in genetic variation, and with very little known about its evolutionary history. This knowledge gap has hampered conservation efforts because hunting has dramatically reduced the species’ once continuous distribution, leaving five surviving gene pools of unknown genetic affinity. Here we examined the range-wide genetic structure of historic and modern populations using the largest and most geographically representative sample of black rhinoceroses ever assembled. Using both mitochondrial and nuclear datasets, we described a staggering loss of 69% of the species’ mitochondrial genetic variation, including the most ancestral lineages that are now absent from modern populations. Genetically unique populations in countries such as Nigeria, Cameroon, Chad, Eritrea, Ethiopia, Somalia, Mozambique, Malawi and Angola no longer exist. We found that the historic range of the West African subspecies (D. b. longipes), declared extinct in 2011, extends into southern Kenya, where a handful of individuals survive in the Masai Mara. We also identify conservation units that will help maintain evolutionary potential. Our results suggest a complete re-evaluation of current conservation management paradigms for the black rhinoceros

Protecting cows in small holder farms in East Africa from tsetse flies by mimicking the odor profile of a non-host bovid

<div><p>Background</p><p>For the first time, differential attraction of pathogen vectors to vertebrate animals is investigated for novel repellents which when applied to preferred host animals turn them into non-hosts thereby providing a new paradigm for innovative vector control. For effectively controlling tsetse flies (<i>Glossina</i> spp.), vectors of African trypanosomosis, causing nagana, repellents more powerful than plant derived, from a non-host animal the waterbuck, <i>Kobus ellipsiprymnus defassa</i>, have recently been identified. Here we investigate these repellents in the field to protect cattle from nagana by making cattle as unattractive as the buck.</p><p>Methodology/Principal findings</p><p>To dispense the waterbuck repellents comprising guaiacol, geranylacetone, pentanoic acid and δ-octalactone, (patent application) we developed an innovative collar-mounted release system for individual cattle. We tested protecting cattle, under natural tsetse challenge, from tsetse transmitted nagana in a large field trial comprising 1,100 cattle with repellent collars in Kenya for 24 months. The collars provided substantial protection to livestock from trypanosome infection by reducing disease levels >80%. Protected cattle were healthier, showed significantly reduced disease levels, higher packed cell volume and significantly increased weight. Collars >60% reduced trypanocide use, 72.7% increase in ownership of oxen per household and enhanced traction power (protected animals ploughed 66% more land than unprotected). Land under cultivation increased by 73.4%. Increase in traction power of protected animals reduced by 69.1% acres tilled by hand per household per ploughing season. Improved food security and household income from very high acceptance of collars (99%) motivated the farmers to form a registered community based organization promoting collars for integrated tsetse control and their commercialization.</p><p>Conclusion/Significance</p><p>Clear demonstration that repellents from un-preferred hosts prevent contact between host and vector, thereby preventing disease transmission: a new paradigm for vector control. Evidence that deploying water buck repellents converts cattle into non-hosts for tsetse flies—<i>‘cows in waterbuck clothing’</i>.</p></div

Farmers perceptions of the effectiveness of the new repellent collar technology.

<p>Farmers perceptions of the effectiveness of the new repellent collar technology.</p

Target used to attract and kill the flies (pull).

<p>(Picture R.K. Saini).</p

Cattle with repellent collars grazing in bush with natural tsetse challenge.

<p>(Picture R.K. Saini).</p

Average number of <i>G</i>. <i>pallidipes</i> flies caught per trap per day (apparent densities) with various tsetse repellent (WRC) treatments over the trial period.

<p>Average number of <i>G</i>. <i>pallidipes</i> flies caught per trap per day (apparent densities) with various tsetse repellent (WRC) treatments over the trial period.</p

Trypanosome infection in cattle with waterbuck repellent compounds (WRC).

<p>Estimates obtained from the generalized estimating equations model. The 95% Confidence Intervals (CI) were constructed using empirically corrected standard errors.</p

Randomized four treatment regimes for the eight trial sites^*.

<p>Randomized four treatment regimes for the eight trial sites^{<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005977#t001fn001" target="_blank">*</a>}.</p

Animal weights with waterbuck repellent compounds (WRC).

<p>Parameter estimates and standard errors obtained from linear mixed model relating animal weight with waterbuck repellent compounds (WRC) treatments over the trial period.</p

Repellent dispenser developed to deliver waterbuck repellent compounds for cattle.

<p>(a) Dispenser with protective shield and (b) without protective shield to show tubing from which the repellent compounds are released and (c) a cow with a repellent collar.</p