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Assessing Mortality of African Vultures Using Wing Tags andGSM-GPS TransmittersAuthor(s): Corinne J. Kendall and Munir Z. ViraniSource: Journal of Raptor Research, 46(1):135-140. 2012.Published By: The Raptor Research FoundationDOI: http://dx.doi.org/10.3356/JRR-10-87.1URL: http://www.bioone.org/doi/full/10.3356/JRR-10-87.1

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ASSESSING MORTALITY OF AFRICAN VULTURES USING WING TAGSAND GSM-GPS TRANSMITTERS

CORINNE J. KENDALL1

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08540 U.S.A.

and

Ornithology Section, Department of Zoology, National Museums of Kenya, P.O. Box 40658-00100,Nairobi, Kenya

MUNIR Z. VIRANIThe Peregrine Fund, 5668 West Flying Hawk Lane, Boise, ID 83709 U.S.A.

and

Ornithology Section, Department of Zoology, National Museums of Kenya, P.O. Box 40658-00100,Nairobi, Kenya

ABSTRACT.—We used GSM-GPS transmitters to study mortality in three species of vultures in Masai MaraNational Reserve, Kenya. GSM-GPS transmitters were a cost-effective alternative to traditional satellitetelemetry. In combination with data from a wing-tagging study, GSM-GPS units provided evidence of highmortality in African vultures, particularly White-backed Vultures (Gyps africanus) and Lappet-faced Vultures(Torgos tracheliotos). Four of seventy-eight wing-tagged vultures were reported dead in a 6-yr period followingattachment, whereas 4 of 17 GSM-GPS-tagged vultures were confirmed dead within a year of attachment,based on collection of dead bird or unit, indicating annual mortality of up to 33% for some species in EastAfrica. Poisoning was confirmed as the cause of death in four of these cases and was suspected in themajority of deaths recorded.

KEY WORDS: White-backed Vulture ; Gyps africanus; Lappet-faced Vulture ; Torgos tracheliotos; GSM-GPS trans-mitters ; mortality; satellite; vulture; wing tagging.

EVALUACION DE LA MORTALIDAD DE LOS BUITRES AFRICANOS USANDO MARCAS EN LASALAS Y TRANSMISORES GSM-GPS

RESUMEN.—Empleamos transmisores GSM-GPS para estudiar la mortalidad en tres especies de buitres en laReserva Nacional Masai Mara, Kenia. Los transmisores GSM-GPS fueron una alternativa eficiente en termi-nos de costo con relacion a la telemetrıa satelital tradicional. En combinacion con datos provenientes de unestudio de marcado en las alas, las unidades GSM-GPS brindaron evidencia sobre una alta mortalidad en losbuitres africanos, particularmente en Gyps africanus y Torgos tracheliotos. Cuatro de los 78 buitres marcadosen las alas fueron reportados como muertos en un perıodo de seis anos luego de la marcacion, mientrasque cuatro de los 17 buitres marcados con GSM-GPS fueron verificados como muertos dentro del ano demarcado, basados en la colecta de aves muertas o de unidades de transmision, indicando una mortalidadanual de hasta 33% para algunas especies en el este de Africa. El envenenamiento fue confirmado como lacausa de muerte en cuatro de estos casos y fue la sospecha en la mayorıa de las muertes registradas.

[Traduccion del equipo editorial]

Banding and telemetry are popular techniquesfor studying dispersal, habitat use, migration routes,and mortality in raptors, but their efficacy is rarely

assessed (Meyburg and Fuller 2007). Recently GSM-GPS transmitters have become available as an alter-native to traditional satellite telemetry. These unitsuse regional cell-phone networks to download GPSdata collected from animals and, thus, data-down-load costs are minimal. Data from GSM-GPS unitsare gathered directly from the global positioning

1 Present address: 113E Eno Hall, Princeton University,Princeton, NJ 08540 U.S.A.; email address: ckendall@princeton.edu

J. Raptor Res. 46(1):135–140

E 2012 The Raptor Research Foundation, Inc.

135

system (GPS), ensuring high accuracy of pointstaken. As a result, GSM-GPS transmitters providesimilar insights into movement ecology, includingrange size, habitat use, foraging behavior, and mor-tality, as do traditional satellite units. GSM-GPStransmitters are particularly ideal for large raptorsthat are likely to traverse large areas, such as vul-tures, and thus come into cell-phone range on aregular basis, even when inhabiting and visiting fair-ly remote areas without coverage. GSM-GPS unitsmay provide more in-depth information aboutmovement than traditional banding or wing-taggingtechniques, but currently there are few publishedstudies demonstrating the use of GSM-GPS transmit-ters on large raptors.

Populations of all six vulture species that arefound in Masai Mara National Reserve, Kenya, havedeclined substantially over the last three decades(Virani et al. 2011). Loss of vultures in East Africais likely to have significant ecological and economicconsequences, and thus conservation of this impor-tant scavenging assemblage is critical (Sekerciogluet al. 2004, Sekercioglu 2006, Markandya et al. 2008,Whelan et al. 2008). Reasons for the populationdeclines are not known, although poisoning, whichoccurs when livestock herders put poisons such ascarbofurans onto wildlife or livestock carcasses in anattempt to kill spotted hyenas (Crocuta crocuta) andlions (Panthera leo) appears to be a major mortalityfactor (Ogada and Keesing 2010, Otieno et al.2010a, Otieno et al. 2010b).

We used two methods—wing tagging and GSM-GPS telemetry—to assess mortality rates and to de-termine causes of mortality. Assessing mortalityrates and causes using telemetry and wing taggingis an important step for the conservation of EastAfrican vultures and helps us elucidate the causesof their declines. Here we compare results fromGSM-GPS transmitters with findings from a wing-tagging study conducted on three species of vul-tures in Masai Mara National Reserve, Kenya.

METHODS

Study Area. East Africa is known for its high wild-life densities and large protected areas, includingNgorogoro Conservation Area, Tsavo East and WestNational Park, and Masai Mara National Reserve(Western et al. 2009). The Mara-Serengeti ecosystemis home to one of the largest ungulate migrations inthe world, with over one million blue wildebeest(Connochaetes taurinus), Burchell’s zebra (Equusburchelli), and Thomson’s gazelle (Gazella thomsonii)

moving between Serengeti National Park, Tanzania,and Masai Mara National Reserve, Kenya, each year.Rainfall is seasonal, with the long rains falling fromMarch to June, and short rains from November toDecember (Ogutu et al. 2008). Migratory herds moveinto the Masai Mara National Reserve from July toOctober. This movement coincides with the dry sea-son, which is a period of particularly high ungulatemortality (Mduma et al. 1999). As a result the Mara-Serengeti ecosystem is arguably one of the most im-portant areas for scavengers in Africa, supportinghigh densities of vultures of many species (Houston2001).

Study Species. Although six species of vulturesare found in Masai Mara National Reserve, we fo-cused on the three largest species for all tagging andGSM-GPS unit attachment, due to the limitationsimposed by the weight of the GSM-GPS transmitters(Houston 1975). Lappet-faced Vultures (Torgos tra-cheliotos) generally feed alone or in pairs and areknown to focus on the tough pieces of meat, includ-ing tendons, skin, and joints. They have largepowerful bills that they use for tearing flesh andopening carcasses (Mundy et al. 1992). Rueppell’sVultures (Gyps rueppellii) and White-backed Vultures(G. africanus; collectively termed Gyps hereafter) areknown for their gregariousness and rapid consump-tion of soft tissues (Houston 1974a, 1974b). Lappet-faced Vultures and White-backed Vultures nest intrees, with particularly high densities of the latternesting along riverbanks in Masai Mara NationalReserve (Virani et al. 2010). Rueppell’s Vulturesare cliff-nesters that nest in cliffs .100 km fromMasai Mara National Reserve, including those atLake Kwenia and Hell’s Gate National Park, Kenya,and the Gol Mountains in Tanzania (Pennycuick1983).

Attachment of Transmitters and Wing Tags. Vul-tures were trapped using nooses, set up as grids orin a line along carcasses (Watson and Watson 1985).Noose grids were made entirely of 90-kg-strengthmonofilament fishing line. Nooses on noose lineswere made of coated wire cord or monofilament,and the noose line was made of parachute cord.Nooses were 10–15 cm in diameter. Noose gridswere generally staked into the ground using tentstakes, whereas noose on noose lines were tied tocarcasses and staked into the ground using 5-cmnails for added stability. Grass or carrion was usedto help hold the nooses upright to increase thechance of a capture. Noose lines and grids consistedof 10 to 20 nooses. Trapping for attachment of

136 KENDALL AND VIRANI VOL. 46, NO. 1

GSM-GPS transmitters was conducted in the MasaiMara National Reserve or surrounding areas. Trap-ping for attachment of wing tags was conducted inMasai Mara National Reserve (01u059S, 34u509E)and in the Athi-Kapiti region, Kenya (01u309S,37u029E). Once a bird was captured, we required5–10 min to process birds for wing tagging and30 min to attach GSM-GPS units. Birds’ eyes werecovered to reduce stress and the handler restrainedboth feet and head.

In 2009, 16 battery-powered GSM-GPS transmit-ters (Africa Wildlife Tracking, Pretoria, SouthAfrica) were attached as backpacks using 11-mmTeflon ribbon (Bally Ribbon Mills, Bally, Pennsylva-nia, U.S.A.). Units weighed between 140 and 160 g,approximately 2% to 3% of the body mass of a givenvulture. Transmitters were programmed to recordlocations four times per d and were expected to last12 mo. We avoided solar-powered units because twosolar-powered satellite units attached in a prelimi-nary study failed within 1 wk, presumably due todamage to the solar units. Backpacks used to attachtransmitters were designed to fall off within a fewyears as recapture of tagged individuals was gener-ally infeasible. Individually numbered plastic wingtags were attached to the patagium of one wingusing cattle ear tags following Wallace et al. (1980).When possible, both wing tag and transmitters wereattached to aid in future identification.

RESULTS

Wing Tag and Transmitter Attachment. We at-tached seventy-eight patagial tags to vultures ofthree species between 2004 and 2009 (Table 1).Of these, 43 were fitted to White-backed Vultures,29 to Rueppell’s Vultures, and 6 to Lappet-facedVultures. Fourteen GSM-GPS transmitters were at-tached to vultures of three species in Masai MaraNational Reserve, Kenya, from May to July 2009.

Of these, five were fitted to African White-backedVultures, five to Rueppell’s Vultures, and four toLappet-faced Vultures. One of the tagged White-backed Vultures was found dead in May 2009 andthe unit was placed on another White-backed Vul-ture in July 2009. In addition, two units were at-tached to Lappet-faced Vultures in May 2010.

Resightings. From 2006 to 2009, there were 71resightings of 26 different wing-tagged individuals,including 13 White-backed Vultures, 12 Rueppell’s-Vultures, and 1 Lappet-faced Vulture. Resightingswere generally made by researchers or by tourguides and were accompanied by photographs forverification where possible. Forty-three of the re-sightings included GPS locations, whereas the oth-ers were descriptions of the location of the sightedbird only. Most resightings occurred in Masai MaraNational Reserve (Table 2). There were four re-sightings outside of the Mara-Serengeti, one eachin Nairobi National Park, Laikipia region, Kiliman-jaro National Park, and Samburu National Park,and all four of these resightings were of Gyps vul-tures that had been tagged in the Athi-Kapiti region.

Mortality Factors. Of the wing-tagged birds, threeadult Rueppell’s Vulture and one White-backed Vul-ture have been reported dead since the beginningof the study. Dead birds were found near ShompoleConservancy in November 2007 (130 km from trap-ping site), Lake Kwenia in December 2010 (150 kmfrom trapping site), Siana Group Ranch along theborder of Masai Mara National Reserve in October2010 (30 km from trapping site) in Kenya and nearGrumeti Game Reserve, Tanzania, in December2010 (120 km from trapping site). People admittedto the use of poison in the case near ShompoleConservancy and tests confirmed that Furadan (acarbamate pesticide) killed the bird in Siana alongthe border of Masai Mara National Reserve. The

Table 1. Numbers and locations of wing tags attached tothree species of African vultures in Kenya from 2004 to2009.

SPECIES

MASAI MARA

NATIONAL RESERVE

ATHI-KAPITI

REGION

White-backed Vulture 25 17Rueppell’s Vulture 27 3Lappet-faced Vulture 3 3

Total 55 23

Table 2. Resightings of wing-tagged vultures by capturesite, Kenya.

CAPTURE SITE

RESIGHTING LOCATION

MASAI MARA,KENYA

SERENGETI,TANZANIA OTHERa

Masai Mara NationalReserve, Kenya 53 8 0

Athi-Kapiti region 5 1 4

a Kilimanjaro National Park, Nairobi National Park, Laikipia, andSamburu.

MARCH 2012 MORTALITY OF AFRICAN VULTURES 137

tagged vulture was one of twenty-one birds killed,including a Hooded Vulture (Necrosyrtes mona-chus), a Bateleur (Terathopius ecaudatus), a TawnyEagle (Aquila rapax), seven Rueppell’s Vultures,and eleven White-backed Vultures. Of the remain-ing three deaths, two appeared to have beencaused by poisoning but causes of mortality wereunconfirmed.

Four of seventeen GSM-GPS-tagged vultures diedwithin the first year of being tagged. Two were adultLappet-faced Vultures and two were adult White-backed Vultures, suggesting an annual mortality of33% for each of the two species. Of these, one wasconfirmed to be poisoned by testing of tissue samples.Based on discussion with locals who disclosed thatpoison had been put on the carcass near the locationof the dead bird, there was circumstantial evidence tosuggest that other deaths also were due to poisoning.Locals told us that poisons such as Furadan typicallywere placed on carcasses of livestock that had beenkilled by lions or hyenas in an effort to kill these pred-ators. In one poisoning event, a spotted hyena, twojackals (Canis mesomelas), one White-backed Vulture,and a Lappet-faced Vulture were killed in addition tothe GSM-GPS-tagged Lappet-faced Vulture that led usto the scene. Three of the deaths were outside pro-tected areas. Deaths occurred in November (n 5 1),April (n 5 1) and May (n 5 2; Fig. 1).

DISCUSSION

Findings from our wing-tagging study indicatedthat Gyps and Lappet-faced Vultures in the regionused a variety of protected areas in addition to theMara-Serengeti ecosystem, including several thatwere more than 200 km from the original trappingsight. At least some researchers believe that vulturepopulation declines documented in Masai Mara Na-tional Reserve represent population declines acrossthe entire southern Kenya-northern Tanzania region(Virani et al. 2011). Like other studies (e.g., Bamfordet al. 2007) in which home range size of adult CapeVultures was found to be about 38 000 km2, our studyconfirmed large individual ranges for all three vul-ture species. All species substantially used nonpro-tected areas, which is likely underestimated bywing-tagging due to under-reporting outside of pro-tected areas (C. Kendall unpubl. data). Other studieshave found similar biases, with tagged or bandedbirds being encountered more often in areas of highhuman settlement (Dykstra et al. 2004). In EastAfrica, there is little western-style birdwatching out-side of protected areas and thus resighting reports,which tend to be from other researchers, tour guides,and tourists, likely are concentrated within protectedareas. In addition, emails via list-servers and postersthat requested for wing-tagging resightings fromtourists and guides were strategically placed at park

Figure 1. Map showing the locations of trapping sites and mortality events for vultures included in this study in Kenyaand Tanzania.

138 KENDALL AND VIRANI VOL. 46, NO. 1

entrances, which would have biased resighting datain favor of vultures seen in protected areas.

Mortality Factors. Poisoning was found to be theprimary cause of death in adult vultures (two ofeight confirmed deaths among adult vulturestagged, with others strongly suspected). Four of 78wing-tagged birds were reported dead in a 6-yr pe-riod, but mortality found using telemetry was signif-icantly higher, suggesting that annual mortality dueto poisoning could be as high as 33%.

Poisoning occurred mainly outside of protectedareas (three of four confirmed instances), makingthe vultures’ substantial use of such areas a majorconservation concern. The majority of poisoningevents occurred during the rainy season, especiallyNovember and May, when human-predator conflictis known to be highest in the region (Kolowski andHolekamp 2006). This period also coincides withlow ungulate density in the Masai Mara, when themajority of terrestrial carnivores are food-stressedand are more likely to depredate livestock.

GSM-GPS Tracking Versus Wing Tagging. In gen-eral, this study suffered from a low resighting rate ofwing-tagged individuals (14 birds per year) due to asmall reporting community in East Africa. However,wing tagging was considerably less expensive than te-lemetry (less than $1 per wing tag), although the num-ber of resightings was low, yielding less than one loca-tion per year per individual tagged, on average. Inaddition to generating data, wing-tagging studies canalso be used to enhance public awareness of vulturesand research efforts as part of the general effort toincrease resightings. For this study, signs about wing-tagged vultures were posted at all gates around MasaiMara National Reserve, Kenya, increasing awarenessamong park rangers, tourists, and tour guides.

GSM-GPS tracking provided detailed data aboutmortality rates and information about mortalityfactors in some cases. New technology using GSM net-works may prove particularly useful for raptor studiesin Africa, given widespread cell-phone coverage therethat covers most wildlife areas, including protectedareas where vultures may concentrate. Although bothGSM-GPS tracking and wing-tagging studies may pro-vide useful information about mortality, the use oftracking may be more appropriate for studies of mor-tality factors that are illegal and thus unlikely to beopenly reported, such as poisoning, and in areas withlimited reporting communities, where resighting ratesmay be low, such as much of Africa.

We recommend that wing-tagging studies be cou-pled with widespread awareness programs, which

should increase the resighting rate of wing-taggedbirds, as well as highlight the importance of vulturesand thus hopefully reduce poisoning rates. Effortsneed to be undertaken to alter human attitudes andbehavior relative to the use of poisons on carcassesif vultures are to persist in East Africa.

Comparison of GSM-GPS and GPS-PTTs. GSM-GPS and GPS-PTT transmitters are typically at-tached as backpacks and thus require similaramounts of time for trapping and fitting animals.Both types of units use the same GPS system torecord locations, with similar quality and accuracyof 5–18 m. However, in addition to location, GSM-GPS units can provide data on velocity that are notalways available with GPS-PTT units. In addition,PTT tags can suffer from radio interference, whichmay limit the number of readings that are receivedin some areas. However, GSM-GPS transmitters areonly effective in areas of good cell-phone networkcoverage or where birds are likely to reliably enterareas of high signal strength. Currently, the primaryadvantage of GSM-GPS-based tracking is the re-duced cost of the units compared with traditionalsatellite tracking, which should allow researchers toincrease sample sizes and statistical power of theirdata. GSM-GPS transmitters are considerably lessexpensive than GPS-PTT units and have lower costsfor data download. GPS-PTT fees vary depending onhow often data are transmitted; low-duty cycles inwhich data are transmitted once a day to a few timesa month are often employed to reduce costs. Thislimits the ability of the researcher to follow the birdin real time for behavioral and other purposes.GSM-GPS transmitters can generally be set to down-load once a day at no additional charge. For thisstudy, it was particularly important to get near-realtime data to establish cause of death and thus GSM-GPS transmitters were preferred.

It should be noted that, due to restrictions im-posed by weight, GSM-GPS transmitters remainacceptable only for the largest raptors (currentlyavailable units have a mass of at least 60 g), buttechnological advancements will likely reduce unitsize and increase battery life, and thus the use ofGSM-GPS transmitters in raptor studies should ex-pand considerably in the near future.

ACKNOWLEDGMENTS

This study was a part of The Peregrine Fund’s Pan Afri-can Raptor Conservation Program and was funded by ThePeregrine Fund, Hawk Mountain Sanctuary, PrincetonUniversity, The Explorer’s Club, and the SeaWorld andBusch Gardens Conservation Fund. We are indebted to

MARCH 2012 MORTALITY OF AFRICAN VULTURES 139

the Narok County Council and the staff of the Masai MaraNational Reserve, in particular the wardens Mr. Sindiyo andMr. Minis for their assistance and permission to conductvulture research in the reserve. We also thank Mr. Koikai,Mr. Lenjirr, and the Cowell family for their help. We aregrateful for the support of the Mara Conservancy and neigh-boring group ranches—Koiyaki, Lemek, Siana and OlaroOrok, and logistical help from Heritage Hotels, Mada Ho-tels, and Africa Eco-camps. We are thankful to Kenya Wild-life Service and the National Museums of Kenya. We thankSimon Thomsett, Keith Bildstein, and the many others whohelped trap the vultures used in this study.

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Received 29 September 2010; accepted 4 October 2011Associate Editor: Keith L. Bildstein

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