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Small mammal communities as indicators of biological integrity Nico Avenant

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Small mammal communities as indicators of biological integrity Nico Avenant National Museum, Bloemfontein, South Africa. C. Schradin. Why small mammals?. Number of organisms: c . 66% of mammals species > 300/ha. Top predators. T.P. Jackson. Prey base. Biomass: > 10% of total

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slide1

Small mammal communities as indicators of

biological integrity

Nico Avenant

National Museum, Bloemfontein, South Africa

C. Schradin

slide2

Why small mammals?

Number of organisms:

c. 66% of mammals species

> 300/ha

Top predators

T.P. Jackson

Prey base

Biomass:> 10% of total

mammalian biomass

Secondary

users

Ecosystem engineers

Prey base

Primary users

Seed dispersers

Soil fertilisers

Primary producers

Growth stimulators

slide3

c. 5% spend >90% of time

under ground

Most small mammals

“secretive”

Superstitions

Public poorly informed

c. 3% spend >90% of time

in disused termitaria

c. 60% are nocturnal

why small mammals
Why small mammals?

* specialized and adapted for survival in “smaller” habitats(than larger mammals) – and are better indicators of ecosystem integrity on the scale that we (e.g. EIA consultants) are working on.

* they are found in comparatively large numbers (a single species up to 200/ha). Rodents are, therefore, more available than larger mammals.

* they are easy to handle, mark indiv’s, monitor movement, etc.

* we know detailed information regarding the biology & natural histories ….

* they reproduce fast (respond quickly to change)

* fairly easy to ID (compared to plants, invertebrates) – teach field personnel

indirectly literature
Indirectly literature …
  • changes in small mammal habitats are associated with changes in small mammal diversity
  • ecological disturbance of these habitats is generally associated with a decrease in small mammal species richness
  • a connection between the presence or absence of small mammal indicator species and disturbance in natural ecosystems

a relatively quick and cheap method of indicating

healthy or unhealthy ecosystem functioning?

slide6

D. MacFadyen

Mice/rats, Shrews,

Elephant shrews

HPH Photography

Shrews

7 species in Free State

W. Lubbe

TP Jackson

slide7

Mice

22 species in Free State

13 species in BFN-area

Mice

slide8

Small mammal survey

Standard method

  • A fixed number of traps (n = 100), are spaced 5 m

apart (e.g. Ferreira & Avenant 2003) , on transects, at each site/plot

  • Baited with a mixture of peanut butter, rolled oats,

sunflower oil and marmite

  • Left open for 4 consecutive nights and days
  • Each trap checked at dusk and dawn;

rebaited when necessary

Sampled by removal trapping

D. MacFadyen

ecotones

Beware

Ecotones
  • Transition zones (ecological link) – area of active interaction between two or more ecosystems.
  • Edge effect – ecotones have different structures than neighbouring communities
slide10

Our concerns are:

  • how to sample and / or monitor small
  • mammal biodiversity,

and then

* to interpret this in terms of ecosystem

integrity.

slide11

Mammal monitoring: -   Density -   Species richness -   Diversity indices (e.g. Shannon, Simpson’s) - Relative abundance or evenness (e.g. Evar) - Reproductive or not - Indicator species (e.g. keystone, pioneer, generalist, specialist) - Indigenous, Endemic & Alien species- Threatened species - Protected species (e.g. CITES)

slide12

Nature reserves:Willem Pretorius NR; Sandveld NR; Caledon NRTussen-die-Riviere NR; QwaQwa NP; Erfenisdam NRConservancies:Korannaberg Farms:Game Farm, Fauresmith; Small stock farm, PhillipolisGlen Agric. Coll.SA Army training base:De Brug Environmental Impact AssessmentsMaguga Dam, Swaziland; Mohale Dam, LesothoLetsa-la-Letsie, Lesotho; CMBSLMaluti-Drakensberg Transfrontier Biodiversity ProjectOther:Ezemvelo Nature Reserve; Namibian Airports

Examples

slide13

Last 12 years:

6 sites; 44 transects

slide14

Example 1 Nature reserve

AVENANT, N.L. 2000. S. Afr. J. Wildl. Res.

slide15

M. minutoides

Rhabdomys

Aethomys

E. myurus

Mastomys

Number of species

2

2

3

2

2

3

2

3

vs 11 / 17

5

korannaberg conservancy
Groups of farms on which the owners collectively practice co-operative nature conservation

Ranger patrols fences, cribs & water pumps

Removes snares

Report mortalities & stray dogs

Prevents unlawful hunting, game & cattle theft

Practices proper problem-animal control measures

Korannaberg Conservancy

Example 2

Increase total proclaimed conservation area in

the Free State Province by c. 6 times

slide19

n = 9

Why?

_ vs 6

slide20

Example 3

Swaziland: Maguga Dam & Hydro-electric scheme

slide22

Table 1 The percentage frequency of grass species, number of herbs, percentage basal cover and Ecological Index value of four plots in the Caledon Nature Reserve, Free State Province, South Africa. EI, Ecological Index; -, not found.

Example 4

Vegetation analysis

Caledon Nature Reserve

*EI, Ecological Index value

*

* Annual grass

* Annual grass

slide23

The percentage contribution of small mammal species trapped on four transects at the Caledon Nature Reserve during four consecutive seasons in 2001/2.

*Significant correlation with EI value (Pearson Product-Moment, p<0.05)

slide24

Our results

Specialists

Species richness

Mystromys

albicaudatus

Diversity

(evenness?)

Number of species

Indicator species

Generalists

Succession

Primary productivity

slide25

some shrubs/trees;

mostly perennials

= climax grassveld

some herbs + shrubs/

trees + more perennials

Number of species

Annuals + more herbs + shrubs/trees + perennials

More annuals + more herbs + shrubs/trees

More annuals + herbs

Annuals

Disturbance

(Time after disturbance – Succession)

Primary productivity

eia s
EIA’s

Constraints: time (=money)

Influence methods:

- type of traps

- trapping period / no. of seasons

- no. of habitats

Rely on Scientific studies

slide28

Significant

seasonal effect

Tussen die Riviere Nature Reserve

AVENANT, N.L. & CAVALLINI, P. 2007. Integrative Zoology

Korannaberg Conservancy

AVENANT, N.L. 2000. Navors.nas.Mus.,Bloemfontein

slide29

Seasonal effect

Mean small mammal species richness and trap success on four grassland plots in the Caledon Nature Reserve, Free State Province, South Africa.

Avenant, Watson & Schulze 2008. Mammalia

slide33

Duration of trapping period

Korannaberg Conservancy

Reached mean maximum number of species after 78 hours (3.25 days) - Avenant 2003. ACIAR Monograph

Caledon Nature Reserve

Avenant et al. 2008. Mammalia

slide34

Duration of trapping period

Tussen die Riviere Nature Reserve

AVENANT, N.L. & CAVALLINI, P. 2007. Integrative Zoology

During all seasons the total number of rodent species (mean = 7 ± 0.8)

were reached between 48 and 96 hours (mean = 3 ± 0.8 days), while

immigration started to have a significant effect from the sixth day

We standardize:

4 consecutive days and nights

slide35

Our results

Specialists

Species richness

Mystromys

albicaudatus

Diversity

(evenness?)

Number of species

Implications …

Indicator species

Generalists

Succession

Primary productivity

slide36

Thank you

Acknowledgements

Field assistants Jacob Senoge, Isak Sekhuni, Pieter Williamson & Jurie du Plessis

Council of the National Museum, Bloemfontein

National Research Foundation

D. MacFadyen

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