K. Yoganand & N. Owen-Smith

Centre for African EcologySchool of Animal Plant & Environmental SciencesUniversity of the Witwatersrand

� Round trip travel between distinct areas

� Highly variable (which makes it most interesting!)

� Various spatial scales – from 30 m (tree frog) to 70,000 km (Arctic tern)

� Time scales - daily (zooplankton) to annual to multiple-year movements (sea turtles)

� Sizes - tiny copepods to huge grey whales

� Mass, synchronized movements (e.g., 1.2 million wildebeest in Serengeti or 65 million red crabs in Christmas Island)

� Often to feed or breed; sometimes to escape

predation

� To exploit spatially discrete resources

� Along a resource gradient (e.g., rain-driven,

altitudinal)

� Mammalian examples include: wildebeest,

saiga, caribou, white-eared kob, springbok

� Affects ecosystem processes:

� Competition and facilitation effects on large

herbivore communities

� Effects on predation pressure

� Nutrient cycling and transport

� Primary productivity

� Grazing effects on fire frequency and tree cover

� Migration may promote and sustain high

abundance

� Migration collapse may lead to population

crash

� E.g., Nairobi National Park, Central Kalahari

Reserve

� Collapses ?

� Lingers on?

� Re-establishes?

� Influences of:

� Regional-scale resource gradient

� Landscape-scale heterogeneity

West-central

(western boundary)

subpopulation

Map from

Joubert (2009)

� Seasonal migratory movements in 1950s, moving southwards from Orpen gate region

� Access to water in Sand river

� Congregations in Ripape seepline grasslands

� Western boundary fencing in early 1960s

Ref: Smuts (1974), Whyte (1985), Whyte & Joubert (1988), Joubert (2009)

� Population crash – >85% decline in this subpopulation by late-1970s, due to:� Loss of access to habitat across the fence

� Exclusion of herds from key wet season grazing on gabbro by a second fence

� Culling and other management interventions

� Combined with a wet decade in 1970s

� Similar interventions on Manyaleti side and similar crash!

� Crash due to combination of post-fencing factors

� Not clear if there was a migration collapse directly linked to fencing, but eventual collapse due to the population crash

� The removal of the boundary fence in mid-

1990s has not brought about population

recovery

� Migration has not been restored to former

levels (at least not visible)

� It has been thought of as a resident sub-

population of wildebeest

� Study period: 2009-2012

� GPS/GSM collars on 10 wildebeest herds

� Hourly locations

� Up to three years of movement data for some

herds

� Habitat maps from satellite imageries

� Intensive field sampling of forage and cover

features

� Classified movements into migratory travel, exploratory visit

and seasonal ranging

� Differences in net displacement (Euclidean distance from

initial location) between successive locations indicated long

and speedy movements and spatial shifts

� Locations within each time segment was used to map

seasonal ranges, using KDE method

� Classified movement strategy of herds into migration,

dispersal, nomadic, etc.

Herd 1 – 2009

Green – wet season range

Orange – dry season range

Lines with arrow –

migratory travel routes

and directions

Herd 2 - 2009

Herd 2 - 2010

Herd 3 - 2009

Herd 3 - 2010

Herd 4 - 2009

Herd 4 - 2010

Herd 4 - 2011

Herd 5 – 2009-10

Wet season

Herd 5 – 2009-10

Dry season

No migration by

this herd, but

showed expansion

of home range

Data from only

6 herds

Pink shaded –

gabbro areas

White –

granite/gneiss

• Onward to dry season ranges – highly variable; return – more synchronous

• Data from only six herds given here (analysis ongoing)

0

1

2

3

4

5

6

7

Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

No

. o

f h

erd

-ye

ar Onward Return

0

1

2

3

4

5

6

7

8

4-8 km 8-12 km 12-16 km 16-20 km 20-30 km

No

. o

f h

erd

-ye

ar

herd_id year movement strategy35 2009 migration

145 2009 migration

145 2010 migration

145 2011 migration

196 2009-10 no migration

196 2010-11 no migration

148 2009 migration

148 2010 Migration

149 2009 Migration

149

…2010

…Migration

…

• Lengthy use of small ranges

0

1

2

3

4

5

6

7

0 100 200 300 400

sea

son

al r

an

ge

siz

e (

km

2)

Duration of stay (days)

� Migratory shifts by many herds from grazing lawns on gabbro and sodic sites to seep-zone (midslope) grasslands on granite or recently burned areas

� The timing of range shifts, length of use of seasonal ranges and distance between seasonal ranges were variable among herds that showed such migration

� Herds that did not show migratory shifts expanded their home ranges in the dry season to encompass seep-zone grasslands

� Most (7 of 9) herds showed migratory behaviour

� Migratory pattern repeated every year

� Distances up to 30 km

� Directional, linear, back-and-forth movements

� No synchronous, mass movements

� Landscape-scale heterogeneity

� No large-scale resource gradient (e. g.,

rainfall-driven)

� Larger population probably meant quicker

resource depletion of small patches and thus

farther movements (in 1950s)

� Facultative migration

� Lengthy use of small, often exclusive habitat

patches by herds

� The current abundance and herd distribution

is inadequate to force resumption of more

extensive migration by this subpopulation

� Augusto Mabunda – for field assistance

� Sanparks Veterinary Services and Helicopter team

� for collaring operations (Peter Buss, Markus Hofmeyr, Johan, Grant

Knight, CharlesThompson)

� Sanparks Protection Services – Richard Sowry and KFI field rangers

� Manyaleti Nature Reserve – Jimmy Thanyani, Mark Bourn and

Dr. Ferreira (Mpumalanga Veterinarian)

� Timbavati Private Nature Reserve – Jacques Britts & Almero Bosch

� Sanparks Scientific Services

� GIS data and support (Sandra MacFadyen and Izak Smit)

� Thembi Khoza, Patricia Khoza and Adolf Manganyi – for liaisoning and

administrative support

� Africa Wildlife Telemetry – for the collars and data downloads

� NRF and University of the Witwatersrand for funding support