small mammals of the bale mountains, ethiopia

A,/;. J . Ecol. 1988, Volume 26, pages 281-294

Small mammals of the Bale Mountains, Ethiopia

D. W . YALD EN Department of Environmental Biology, University of Manchester. M I 3 9PL, U.K.

Summary A sample of 535 small mammals, caught over a range of altitudes from 1500 to 4000 m in the Bale Mountains, on various expeditions from December 1971 to August 1986, enables the altitudinal zonation of the species to be delimited. The most abundant species, Lophuromys javopunctatus, ranged from near the lower tree line at 1550 m, right up through the forested zones and onto the Afro-alpine moorland at 3900 m. The endemic Praomys albipes also ranged through the forest from 1550 to 3200 m, but was replaced in open habitats between 2400 and 3900 m by Stenocephalemys griseicauda and between 3000 and 4000 m by S. albocauduta, which was relatively more abundant than its congener at higher altitudes. Other moorland species, including Crocidura , fumosa, Oromys typus, Lophuromys melanonyx and Arvicanthis blicki were also commonest at 3800-4000 m, but, like the Stenocephalemys spp., penetrated to lower altitudes in open habitats. Mus mahomet was confined to lower altitudes (1 51&3000 m) and open habitats, apparently replaced by Mus triton, not previously recorded from Ethiopia, in forested habitats at middle altitudes (1950-2400 m).

RCsumi Grgce a un echantillonnage de 535 petits mammiferes prklevks a une gamme d’altitudes variant de 1500 a 4000 m, dans les Bale Mountains lors de diverses expkditions, de dlcembre 1971 a aoi3 1986, on a pu delimiter une repartition des especes selon l’altitude.

L’espece la plus abondante, Lophuromysjavopunctatus, se rencontrait depuis pratiquement la plus basse ligne arboree, a 1550 m, a travers toutes les zones forestieres jusqu’aux bruyeres afroalpines a 3900 m. Praomys albipes, endttmique, se recontrait aussi a travers la for& de 1500 a 3200 m, mais etait remplacke dans les habitats decouverts entre 2400 et 3900 m par Stenocephalemys griseicauda et entre 3000 et 4000 m par S. albocaudata, qui est relativement plus abondant que sa congknere a de plus hautes altitudes. D’autres especes caractkristiques des bruyires, dont Crocidura . fumosa, Otomys typus, Lophuromys melanonyx et Arvicanthis blicki ktaient aussi les plus frequentes a 3800-4000 m mais, comme les Stenocephalemys spp., penetraient les habitats ouverts des plus basses altitudes. Mus mahomet restait confinie aux basses altitudes (1510-3000 m) et aux habitats ouverts, remplacke, semble-t-il, par Mus triton, non encore signalee en Ethiopie, dans les habitats forestiers de moyenne altitude (195&2400 m).

Introduction The small mammal (rodent and insectivore) fauna of Ethiopia contains at least ten endemic species (perhaps fifteen depending on taxonomic authority), yet has

28 1

282 D. W. Yalden

received little ecological study. Most papers consist of faunal lists, providing distributional data, which have been summarized by Yalden, Largen & Kock (1976). The two major ecological contributions are Miiller's account of Arvicanthis abyssinicus in Simien (Muller, 1977), which includes some information on other species as well, and Rupp's posthumously published account of his collecting over a wide area of southern Ethiopia (Rupp, 1980; see also Hutterer, 1981). Rupp (1980) presented an invaluable analysis of rodent distribution and habitat, with particular emphasis on altitudinal zonation and the endemic species. His account was a composite one, and although it included a sample of ninety-two rodents from the mountains of Bale Province, he collected there only at a limited range of altitudes between 3000 and 3300 m. As a result of three collecting expeditions between 1971 and 1986 involving the present author, and collections made locally in 19841985, it is possible to present an account of the altitudinal zonation of small mammals in Bale which supplements and extends Rupp's account. In particular, there are collections made at high altitude in the Afro-alpine moorland, and the first ever collections from the Harenna Forest on the south side of the mountains.

Material and locations (1) 1971-1972 Expedition. Between 16 December 1971 and 11 January 1972, an expedition led by Dr P. Morris, including also Dr M. J. Largen, Dr B. M. G. Jones and D.W.Y., collected 205 small mammals. They collected mostly around Dinshu (07'06'N 30"46'E, alt. c. 3100 m), but also at Garba Garacha and in the Worgona (Urgana) Valley at 3850 and 3940 m (Fig. 1). (2) 1975 Expedition. A further expedition organized by Dr P. Morris collected at a number of sites in SE Ethiopia between 30 March and 4 May 1975; a short period from 16 to 19 April was spent trapping along the (then) new road south from Goba, along an altitudinal transect between 3200 and 3800 m (c. 06'53" 40"03'E). Dr B. M. G. Jones, Dr M. J. Largen, I . R. Beames, Dr D. Corke and D.W.Y. were members of this expedition. A sample of forty-three mammals was collected in this area of the Bale Mountains. (3) 1986 (Harenna Forest) Expedition. The new road from Goba now extends across the plateau at over 4000 m, and then descends through the Harenna Forest on the south side of the Mountains to D o b M e n a (Masslo) at 1250 m, and on to the bridge over the Ganale River (the Sidam-Bale bridge). The 1975 expedition tried to make this journey, but the road was not then complete. Dr J. C. Hillman, attached to the Ethiopian Wildlife Conservation Organization (E.W.C.O.) and funded by the Wildlife Conservation International of the New York Zoological Society, organized an expedition to the Harenna Forest as part of the planning of the Bale Mountains National Park (Hillman, 1986). Dr M. J. Largen, D.W.Y. and fifteen others (from E.W.C.O. and Addis Ababa University) participated in this expedition, which used the now completed road to investigate the altitudinal zonation of both flora and fauna through the forest. Inter alia, a sample of 192 small mammals was obtained. (4) Bale Mountains National Park collection. During his stay at Dinshu in 1984- 1985, at the Park Headquarters, Dr J. C. Hillman collected small mammals, mostly around Dinshu at 3 170 m but also along the new road across the Sanetti Plateau at 4050 m. He obtained a sample of ninety-one mammals.

Small mammals, Ethiopia 283

All trapping used snap-traps (‘Nipper’ and ‘Little Nipper’) set at approxi- mately 10 m intervals. Traps were baited with peanut butter and rolled oats, and checked twice daily. On the Harenna Forest Expedition, large and small traps alternated at trap positions, but this regime was not strictly followed on earlier expeditions.

Material from the three expeditions is now deposited in the British Museum (Natural History), the Liverpool Museum, and the Natural History Museum, Addis Ababa.

Habitats The vegetation zones in the Bale Mountains were discussed by Brown (1969) during his pioneering census of the Mountain Nyala Tragelaphus buxtoni, and a detailed account of zonation in the Harenna Forest will be prepared by the botanists on the expedition, Dr Mesfin Tadesse and Ato Lissanework Nigatu. The following brief account is based on their preliminary notes and on Brown’s paper. It should be noted that Brown confused the peak of Little Batu (c. 3800 m) with Batu proper (4203 m), and consequently misplaced many localities; neither modern

284 D . W, Yalden

maps nor satellite photographs were available to him, and even Dinshu was barely accessable by road (Hillman, 1985). This does not affect the value of his notes on habitat. More seriously his conversions of altitude from feet (which seem correct) to metres seem to have used a ratio of 0.31, rather than 0.3048, and all his metric altitudes are about 200 m too high.

In the Harenna Forest, on the south side of the Bale Mountains, we recognized the following zones:-

(1) Combretum-Terminalia scrub, below 1550 m. (2) A sharp lower tree line at 1550 m marks the lower limit of the Harenna Forest,

occupied by a belt with Podocarpus gracilior as the characteristic tree. (3) At 1900 m, a belt of Aningeria forest begins, with A . ado&-friederici and A .

altissima as characteristic species. (4) At 2350 m, a zone with Scheflera abyssinica and Hagenia abyssinicu as

characteristic dominant trees begins. (5) Above 2600 m, Hagenia is more numerous than Scheflera, and Erica urboreu

appears. (6) Above 3000 m, up to a sharp upper treeline at 3250 m, Erica arborea is the

dominant tree, with Hypericum revolutum and Rappanea simensis also numerous.

(7) Above the tree line at 3250 m, a shrubby form of Erica arborea, probably produced by fire, is dominant.

(8) Above 3850 m, the break in slope at the southern edge of the Sanetti Plateau marks also the transition between the Erica bush and the open Afro-alpine moorland, with Helichrysum citrispinum, A fchemilla spp. and Lobelia rhynchopetalum.

On the southern side of the mountains the rainfall is high, and the higher part of the forest (above 2400 m) is cloud forest with abundant epiphytes. To the north, the climate is much drier, and Juniperusprocera is the dominant tree between 2900 and 3000 m; thus the Scheflera-Hagenia zone of the south is largely replaced by a Juniperus zone in the north. Below 2900 m, there is an open grassy plateau, which has no equivalent in the south. Above the Juniperus zone, Brown (1969) recognized Hagenia-Hypericum forest between 3000 and 3 170 m, Hypericum forest between 3170 and 3350 m, and Erica arborea forest from 3350 up to 3445 m, the upper tree line. South of Goba, we thought the treeline (between Hypericum forest and Erica bush) to be at about 3300 m.

This forest zonation is modified by various clearings, some natural but others partly or entirely anthropogenic. Among those in the Harenna Forest are a natural clearing, the Shawe swamp, at 1950 m, and a larger clearing, probably partly anthropogenic, at 2400 m (this is at Katcha, which was the base camp site for the 1986 expedition). On the north side, the wide river valleys, especially of the Danka and Web Rivers, are tongues of open grassland extending through the forest, joining the open moorland above to the grassland plateau below. These various clearings have important effects on the distribution of some of the small mammals.

Taxonomy In the following account, nomenclature mostly follows, conservatively, the names used by Yalden et al. (1976) in the Catalogue of Mammals of Ethiopia, in which


Table 1. Small mammals caught in the Bale Mountains, 1971-1986. (Abbreviations for Fig. I and Table 4) Habitats: F-Forest; G-Grasslands; M-Moorlands. Measurements are given as a general indication of the size of each species (Wt, g; others, mm); juveniles were excluded in calculating these means

Body Measurements Total Altitudinal

caught Range(m) Wt HB TL HF EA Habitat

Crocidura fumosa (C.$) C. haileyi (C. ha.) C.,flavescens (C.,p.) C. sp. B (C.B.) C. sp. A (C.A.) Mus mahomet ( M . m . ) M . triton (M.1.) Arvicanihis blicki ( A h . ) A . dembeensis ( A d . ) Praomys alhipes (P .u . ) St enocephalemys

grisricauda (S .g . ) S. albocaudaia ( X u . ) Lophuromgs

L . melanongx ( L m . ) Oromys ~ypupus (0.1.) Tachyorycres

splendens ( T.s.) T. murrocephalus (T .m.) Dendronius lovali (D.1.) D. mystacalis (D.m .)

,flavopunciatus ( L J )

78 10 3 3 6

14 14 19

I 103 68

34 I36

I I 18

1

7 5 4

240Ck3900 300M050 195&2400 240&3200

2400 151Ck3000 195(t-3000 3 I OM050

1510 I5 I &3200 240Ck3900

300M050 15 1 s 3 9 0 0

3 IO(t4050 300M050 240MOOO

3 I OM050 300Ck3 100 240&3 100

19 93 60 17 14 85 53 16 30 115 72 19

3 54 44 11 9 71 47 13

10 70 52 14 16 84 65 17

128 161 100 31 80 135 112 31 49 123 153 27 99 153 143 30

137 I64 139 33 52 118 61 22

107 147 75 28 100 158 76 26 194 180 62 30

597 261 56 35 12 72 73 19 I I 68 89 20

I I I I 12 7 9

12 14 19 17 22 24

21 17

20 21 12

12 15 15

G-M M G G F G F

M G F G

M F

M G-M

G

M G G

Total 535

material collected on the 1971-1972 and 1975 expeditions is mentioned. Both Hutterer (1981) and Dippenaar (1980) suggest that material from Bale which we turned Crocidura fumosa should be distinguished as C. glassi or C. thalia, and Dippenaar (1980) further suggests that our material of C. baileyi should be distinguished as c. lucina. Further additions to the shrew fauna of Ethiopia, and changes in nomenclature, are proposed by Hutterer in other papers (Hutterer, 1983, also in Demeter, 1982); these changes require more detailed consideration than is appropriate here. However, we found two small Crocidura in the Harenna Forest, though we had not collected small shrews in Bale on previous trips. Hutterer (198 1) has identified two small shrews occurring sympatrically at Addis Ababa, but suggests (pers. comm. 1987) that these Harenna Forest species are not the same as those. They will therefore be referred to simply as Crocidura sp. A and sp. B.

Results Zonation A summary of our results is presented in Table 1, and a diagrammatic represen- tation of the altitudinal zonation in Fig. 2. Two species, the endemic Praomys

286 D . W . Yalden

n

u - :- u-

El--


Tnble2. LophuromysPuvopuncrurus. Relative head-and-body (HB) and tail length (TL) of specimens from Bale and Kaffa provinces

Site HB TL TL/HB%

S.W. Forest (Kaffa) I500m Yadot/Shisha I540m Shawe R. 1950m Katcha 2400m Dinshu area 300G3 lOOm Above Goba 3300m Above Rira 3330m Worgona Valley 3900m

121 k 11.3

123* 4.3

121 * 4.9

117k 8.2

117k 7.9

118+ 4.9

113k 7.5

119k 4.6

72.9k 7 . 0 a

7 9 k 4.4

7 7 k 11.2

71.0+ 9.5 *

59.9k 6.7

57.4k 5.0

63.0+ 2.8 *

59.4k 3.1

60.2

64.2

63.6

60.7

51.2

48.6

55.8

49.5

n = I5

n = 3-5

n = 5-7

n = 14-17

n = 17-20

n = 5

n = I 5

n = 8

Asignificantly different, r=6.06, P<O.OOI; 'Significantly different, r=3.03, P< 0.01.

albipes and the harsh-furred rat Lophuromysflavopunctatus were much the most common rodents, particularly in the Harenna Forest. Both occurred from the lowest site within the forest, at 1550 m, up to the upper tree line at 3200 m, but L. ,fEavopunctatus extended further into the Afro-alpine moorland zone at 3850 m; at these higher altitudes, it was always associated with clumps of Erica arborea and Philippia abyssinica. Rupp (1980) drew attention to an apparent cline in size with altitude in L.flavopunctatus; comparing samples from different sites in Ethiopia, he suggested that animals from the south west (1 700 m, Jimma area) were larger and had longer tails than those from higher altitudes both in Bale (3000-3200 m) and bongke, Gemu-Gofa (also 3000-3200 m). However, he did not test these differences statistically. Within the Bale samples, the trend to shorter tails at higher altitudes is also present, and, for sites with adequate samples, is statistically significant (Table 2). Our own sample from the forests of SW Ethiopia, collected in January 1971 at 1500 m, also differs significantly in tail length from the Worgona Valley sample collected in January 1972 at 3940 m. Differences in head-and-body length are, however, not significant. This result is relevant, as Rupp (1980) remarks, to the taxonomic status of the high-altitude L. brevicaudus Osgood, which we have already subsumed into the synonomy of L. flavopunctatus (Yalden et al., 1976).

At higher sites, P. albipes overlapped in altitudinal distribution with the larger Stenocephalemys griseicauda, but the two species were separated ecologically; P. albipes was associated with the forest, while S. griseicauda was confined to more open sites, for example at the edges of clearings. This was especially evident at Katcha, the lowest site (at 2400 m) where we caught S. griseicauda. On a grid of 49 traps (see later) set entirely within the forest, we caught 15 P. albipes but no S .

288 D. W. Yalden

Table 3. Relative abundance of Stenocephalemys spp. above and below 3500m

240C3300m 380W000m Total

S. griseicauda S . albocaudata

65 3 68 10 24 34

X = 88.9. P < O . O O I .

griseicauda, yet in trapping elsewhere at Katcha, mostly around the edge of the clearing, we caught 16 P . albipes and 11 S. griseicauda. Above 3000 m, S. griseicauda overlapped with its congener S . albocaudata, but these two species also appeared to be separated by habitat and certainly differed in their altitudinal preference. S . griseicauda was more numerous at lower altitudes (2400-3300 m), apparently in bushy areas, whereas S. albocaudata was most abundant at higher altitudes (380MOOO m), on the Afro-alpine moorland (Table 3). S. albocaudata shared its preference for moorland with a number of other moorland specialists: Lophuromys melanonyx, Arvicanthis blicki, Tachyoryctes macrocephalus (all four being Ethiopian endemics) and perhaps also Otomys typus. All of these species extend their range to lower altitudes on the northern side of the mountains, at 3000-3100 m around Dinshu, and appear to have done so by penetrating the forest zones along the open areas of the river valleys. Similarly, the occurrence of S. griseicauda at Katcha was associated with the large clearing there, and we had indications (but failed to obtain an adult specimen to confirm it) that Otomys typus also occurred at Katcha. One species, Dendromus lovuti, appears to be a specialist high-grassland endemic.

The ecological relationship between L. melanonyx and A . blicki deserves further study, since they appear to live in mixed colonies, and seem to use the same high-pitched alarm call to warn neighbours of danger. In January 1972 when L. melanonyx had not been described) we collected both species at two different sites, and were unaware that we had two species. We assumed that the smaller L. melanonyx were simply juvenile A. blicki. The deception was enhanced for us, as field collectors, by the fact that L. melanonyx has a tough skin, like most mammals including A . blicki, not the very fragile skin which is so characteristic of L. Javopunctatus. Presumably, like the rest of the genus (Dieterlen, 1976), L. melanonyx is insectivorous, while A. blicki may be more herbivorous, but this needs to be confirmed.

At the lowest levels, Mus mahomet was common in the Combretum-Terminalia scrub, below the Harenna Forest, and occurred within the forest at other open, grassy sites, along the roadside and, particularly, at the swamp near the Shawe River (at 1950 m). On the north side of the mountains, isolated specimens have been obtained, again in open areas, as high as 3000 m, and one possibly at 3300 m, near Dinshu. In the Harenna forest, M . mahornet overlapped vertically with another Mus species, a distinctive, olive-brown species, which had not been previously caught by us. This appears to be Mus triton, by comparison with the type and other material from Kenya, Uganda, Tanzania and Malawi in the British


Museum (Natural History). It is also, from his description, the form referred to as ‘Mus sp. nov.’ by Rupp (1980), who caught one specimen just south of Goba. In Harenna forest, this form was moderately numerous at Katcha, 2400 m, but was largely confined to the forest proper; it was also obtained at the Shawe area (1950 m), in forest, and as a commensal in Rira village at 3000 m. The preference of M . triton for forest habitats obviously separates it ecologically from M . rnahomet. The capture of a single specimen of Arvicanthus dembeensis below the tree-line in the Combretum-Terrninalia scrub at 15 10 m emphasizes its separation, by 1500 m in altitude and the whole of the forest zone in habitat, from its congener A . blicki.

Among the shrews, Crocidura fumosa shows a distribution like that of S . griseicauda-higher altitude, open vegetation from 2400 to 3850 m; it was much more common than the other shrews and was, indeed, the third most common small mammal. C. baileyi appears to be a moorland or moorland-grassland species, confined to altitudes above 3000 m. The other three species were obtained only in small numbers, well below the treeline, and in association with either clearings (C.Jluvescens, Crocidura sp. B) or within the forest (Crocidura sp. A). The ecological separation of the two small species at Katcha was the same as that between P. albipes and S. griseicauda; nearly all of the Crocidura sp. A were caught on the grid set in the forest, where Crocidura sp. B, like S. griseicauda, was not caught at all.

Abundance

We have two indications of the relative abundance of small mammals in the Bale area. For most sites we can express our catch as number of small mammals caught per 100 trap nights (though the data on trap nights are not available for the 1971- 1972 expedition); these data can also be compared with Rupp’s (1980) information. In addition, at four sites in the Harenna Forest we set grids of 7 x 7=49 traps, spaced at 10 m intervals and therefore covering a trapping area of 0.49 ha, for three nights. Thus for those grids we can produce a crude density index and, for two of them, estimate the total small mammal population using Zippin’s (1956) method. These grids were set to sample each of the four main forest zones.

In the Harenna Forest, the main trapping sites at 195C2400 m yielded trapping successes of 2627% (Table 4). These were moist forest sites, with good ground cover, and were therefore expected to yield good catches of small mammals. The two lowest sites, in the dry Podocarpus forest and below the lower tree line, were much less successful (below 10% trap success), and recall the very poor trap success at low altitude in SE Ethiopia obtained by Rupp (1980): 0% in 300 trap nights near Neghelli and 3.3% in 120 trap nights near the Genale River. Our own trapping near Neghilli in 1975 was also poorly rewarded-2.7% in 741 trap nights. Collectively, these results suggest that the low productivity associated with much lower rainfall is reflected, as expected, in low populations of small mammals.

In the Harenna Forest, the highest of the four grids, at 3280 m in Erica forest, also yielded few mammals, but this cannot be interpreted as a similar reduced productivity because of lower temperatures, since the even higher trap line in Erica scrub at 3330 m was the most successful trapping site of all, with 38.9%. In addition, trapping at high altitude south of Goba in 1975 yielded, combining the three sites, a trap success of 19% (Table 4); Rupp (1980) achieved 35% trap success

h,

\o

0

Tab

le 4

. Cat

ches

and

trap

ping

suc

cess

at m

ajor

site

s in

the

mou

ntai

ns of

Bal

e Pro

vinc

e, E

thio

pia.

Abb

revi

atio

ns o

f spe

cies

as in

Tab

le 1

P Si

te

Yea

r (m)

Nig

hts

CJ

C.b

u. C

.A.

M.m

. M

.t.

A.6

. P

.u.

S.g

. S

.U.

LJ

L.m

. 0.1.

Oth

ers

Tot

al

(Yo)

7

Trap

ping

A

ltitu

de

Tra

ps

succ

ess

w

Bel

ow F

ores

t Sh

isha

(G

rid 1

) Sh

awe

(Grid

2)

Shaw

e

Kat

cha

(Grid

3)

Kat

cha

(Cle

arin

g)

Web

Riv

er

Din

shu

area

7k

m S

. Gob

a lO

km S

. Gob

a A

bove

Rira

(G

rid 4

) A

bove

Rira

(E

rica

bush

) 17

km S

. Gob

a W

orgo

na V

alle

y Sa

netti

Pla

teau

(Sw

amp)

1986

19

86

1986

1986

1986

1986

1971

19

71

1975

19

75

1986

1986

1975

19

71

1985

1510

15

50

1950

1950

2400

2400

3000

31

00

3200

33

00

3280

3330

3800

39

00

4050

90-

147

-

145

-

40-

140

-

206

4

? 32

?

27

168

1 20

-

147

1

90

6

20 -

?7

80

-

-

I-

26

- -

9-

-

5-

15

- -

10 - -

-

7-

16

I1

-

10 - -

- I

--

3

7 3

14

-3

6

21

29

7 50

2

I1

14

9 -

2-

-

1-

2

-

1 I

--

_-

_

_-

-

--

_

__

__

-_

2-

8

-

19 - -

--

3-

1

4 4

-

1 -

_

5-

2

19

9

4 1

_-

3

--

1

-

51

__

A.d

.1

8 9 36

c.fl.1

7 34

C.fl

.2 C

.B.2

D.m

. 1

55

D.1

.3

75

T.s.1

T.m

.1 D

.1.2

D.m

.2

159 26 4

D.m

.1

4*

35

13

T.m

.4

51

11

c ::;

9 24

.8

17.5

24.3

26.7

? ? 15

.5

20-0

2.

7

38.9

65.0

? 13

.8

Tota

l 78

10

6

14

13**

19

98

** 6

8 34

13

6 11

18

21

52

7

*Tot

al in

clud

es 1

Gru

phiu

rus m

urin

us. *

*Tab

le I

has s

light

ly d

iffer

ent t

otal

s fo

r the

se sp

ecie

s bec

ause

a s

mal

l num

ber o

f ext

ra sp

ecim

ens.

colle

cted

by

hand

or f

rom

sm

all

trapp

ing

sess

ions

, are

incl

uded

ther

e.

Small mammals, Ethiopia 29 1

in the same area. The low success in the Erica forest is, therefore, not likely to be due to an effect of altitude or temperature, but is a particular characteristic of this site. It was, in fact, near the village of Rira, and appeared to have suffered severely from grazing by livestock (cattle, sheep and horses) so that rather little ground cover remained.

Estimation of population size and standard error by Zippin’s method depends on the catch declining on successive occasions. This assumption was not met on Grid 1, at Shisha (catches of 0 ,3 and 6 on successive nights) nor on Grid 4, above Rira (catches of 0,O and 4). The other two grids yielded catches of 14, 10 and 10 on Grid 3, at Katcha-giving a population estimate of 80.9& 12.5-and 21, 9 and 6 on Grid 2, at Shawe-giving a population estimate of 42-3 k 1.34. At both sites, P . albipes and L. Javopunctatus were the most numerous species, but Mus triton was also caught on both grids and Crocidura sp. A on Grid 3. The total weight (biomass) of these catches was 1258 g on Grid 3 and 1565 g on Grid 2. These biomass estimates are only about half of the lowest values obtained for Arvicanthis abyssinicus at 3700 m in Simien by Muller (1979), who estimated values from 4900 g ha-‘ in May up to 16,500 g ha-’ in FebruaryIMarch. An alternative calculation, using the population estimate of eighty-one small mammals for Grid 3, at Katcha, and the mean weight of 37 g for each capture there, gives a projected biomass of 61 16 g ha-’, which is within the lower part of Miiller’s range of figures. That population estimate, with its large standard error, is more suspect than the one for Grid 2, and it seems more likely that rodents are genuinely less numerous, and contribute to a lower biomass, in the forest zones than in grasslands or moorlands. If there was an ‘edge effect’ round our grids, the effective trapping area was actually larger than 0.49 ha, and the density therefore less, but we cannot guess how much less.

Nocturnalldiurnal behaviour Traps were checked early morning and late afternoon in the Harenna Forest; animals caught in the afternoon had certainly been active during daylight, whereas those caught in the morning had mostly been nocturnal, though some could have been active in the early morning. Table 5 presents the relevant data for four sites with reasonable samples. It is clear that P . albipes and S. griseicauda are largely or exclusively nocturnal, while some L. Jlavopunctatus and Mus triton are certainly diurnal. With the very cold nights at high altitude, one might expect nocturnal activity of small mammals to be reduced but there is no evidence of this in these figures; furthermore, we noted in 1972 in the Worgona Valley that S. albocaudata was exclusively nocturnal, though the detailed data to demonstrate this are not now available. However, from observations, A . blicki and L. melanonyx seem to be predominantly diurnal, as is T. macrocephalus (Yalden, 1975).

Additional species A few additional species were recorded casually, either caught by hand, or at sites where too few mammals were caught to enable any worthwhile comment to be made on altitudinal zonation or habitat preference. The common mole-rat Tachyoryctes splendens was certainly present at Katcha, from the evidence of mole- hills and tunnels, but no specimens were obtained, and a single specimen was

292 D . W . Yalden

Table 5. Catch of small mammals in morning (am) and evening (pm) trap rounds (indicating nocturnal and diurnal activity, respectively) at four major sites in the Harenna Forest area, 1986

Shawe Grid 2 Katcha Grid 3 Katcha other Above Rira ( 19504 (2400m) (2400m) (333Om) Total

am pm am pm am pm am pm am pm

P. albipes 21 I I5 0 16 0 0 0 5 8 1 S. griseicauda 0 0 0 0 I 1 0 8 0 1 9 0 M . triton I 0 1 4 5 2 0 0 7 6 L..fkrvopunctatus 7 2 I 3 5 5 12 7 31 17 A . hlicki 0 0 0 0 0 0 1 I I I Crocidura spp. 0 0 3 1 7 2 5 I 1 5 4

Total 35 3 26 8 4 4 9 26 9 130 28

obtained near Dinshu; skulls were also found in owl pellets in the high moorland (Yalden, 1973) though they could have been imported from lower levels. A small mouse, Dendromus mystacalis, was caught three times, near Dinshu, at Katcha, and on Grid 4 above Rira, while just the tail of a dormouse Graphiurus murinus was also caught on Grid 4. We failed to trap any Megadendromus nikolausi, another endemic rodent recently described from this area (Dieterlen & Rupp, 1978).

Discussion In most respects, the altitudinal zonation recorded in Bale and the habitat preferences recognized accord well with what Rupp (1980) has already described on a composite basis. In particular, the restriction of P . albipes to forest and forest- edge habitats at middle altitudes, and its replacement by S. griseicauda in shrub habitats at higher levels, matches his results, and also those obtained by Muller (1977). Rupp (1980) did not trap in the high Afro-alpine moorland, and was therefore not able to detect the further replacement of S. griseicauda by S . albocaudata at still higher altitudes, nor could he comment on the obvious preference of L. melanonyx, A . blicki and T. macrocephalus for this high zone (though Yalden, 1975, has already described this for T. rnacrocephalus). Our association of D. lovati with the high altitude grassland agrees with both Muller (1977) and Rupp (1980).

At the lower limit of the forest, both P . albipes and L. Jlavopunctatus extend down toward the lower tree line at 1550 m but not, apparently, beyond it. This accords well with the lower limit drawn by Rupp (1980, fig. 17), but it should be noted that in SW Ethiopia P . albipies has been recorded as low as 820 m in the Godare Forest, and L.Jqavopunctatus at 1220 m in the Manera Forest. Yalden et al. (1976), drawing attention to these records, suggest that low rainfall, rather than, for example, high temperature, is presumably setting the lower limit for these species. South-west Ethiopia is characterized by higher rainfall than the rest of the country, and, therefore, by extensive rain forest at relatively low altitudes.

A surprising feature of the Harenna Forest is the apparent poverty of the small mammal fauna. In the forest proper, only five species ( P . albipes, L.Javopunctatus,


M . triton, Crocidura sp. A and possibly Graphiurus murinus) were present; species associated with more open habitats within the forest (C. fumosa, C. Jlavescens, Crocidura sp. B, S. griseicauda, M . mahomet and perhaps D . mystacalis) brings the total to only eleven species, seven rodents and four shrews. In the Jimma area, Rupp (1980) recorded ten rodents and at least one shrew (CrociduraJlavescens, see Hutterer, I98 1) and other shrews certainly occur. Six additional rodents, Oenomys hypoxanthus, Lemniscomys striatus, Pelomys harringtoni, Grammomys dolichurus, Dasymys incomtus and perhaps Praomys natalensis, are known from the south- west forests, and at least two (Pelomys harringtoni, Praomys natalensis) are known from east of the Rift Valley in Ethiopia (the Rift Valley being a major zoogeographical barrier in Ethiopia). In their analysis of forest birds in Africa, Diamond & Hamilton (1980) suggest that the forest fauna of Ethiopia is impover- ished, and interpret this to indicate that forest was greatly reduced during the cold, dry periods corresponding to the glacial periods of the Holarctic. The apparently poor small mammal fauna in the Harenna Forest may, therefore, represent a more extreme manifestation of the same phenomenon. The fact that most of the endemic Ethiopian mammals ( A . blicki, L . melanonyx, S . griseicauda, S. albocaudata, T. macrocephalus, D. lovati, C. baileyi, among those recorded here) are characteristic of high-altitude moorland and grassland may indeed argue for the complementary view, that such habitats were well developed and persistent in Ethiopia throughout the Pleistocene.

Acknowledgments

The collections detailed here were only obtained with the enthusiastic help of all the other members of the expeditions, but in particular Dr P. Morris, who organized both the 1971-1972 and 1975 expeditions, is owed a special debt of thanks. Similarly, Dr J. C. Hillman organized the 1986 expedition, and kindly shared data from his collecting around Dinshu. Financial help for the various expeditions came from several sources, including the Royal Society of London, Wildlife Conservation International of the New York Zoological Society, the University of Manchester, the Percy Sladen Trust and the Godman Fund. The 1986 expedition was undertaken at the invitation of Ato Teshome Ashine, Manager of E.W.C.O., to whom warm thanks are due. Drs J. C. Hillman, M. J. Largen and P. Morris made helpful comments on the typescript, and Mrs S. Hardman kindly typed it.

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(Manuscript received 10 November 1987; revision accepted 25 March 1988)

small mammals of the bale mountains, ethiopia

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