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Mamm.bioi. 66 (2001) 111-115 MammaNan Biology ^^fe- © Urban & Fischer Verlag I^^Sl http://www.urbanfischerde/journals/mammbiol Zeitschrift für Säugetierl

Short communication

Reproductive ecology of the endangered monogamous Malagasy giant jumping , antimena

By Simone Sommer

Zoologisches Institut und Museum, Universität Hamburg, Hamburg

Receipt of Ms. 11. 05. 2000 Acceptance of Ms. 06. 10. 2000

Key words: Hypogeomys antimena, reproductive ecology, Madagascar

Hypogeomys antimena, the Malagasy giant Short birth intervals and sexual maturation jumping rat, is the largest extant endemic at an early age (Hasler 1975). of Madagascar. Both sexes are ca. In Order to increase our very limited knowl-

30 cm long and weigh ca. 1.2 kg. It is consid- edge of the biology, ecology, and behaviour ered to be one of the most endangered of H. antimena and for conservation pur- mammahan of Madagascar. The dis- poses long-term field studies were initiated tribution of this rodent has greatly dimin- in 1992. It turned out that H. antimena has ished during the past two millennia. The last some very unusual hfe characteristics for a

remaining population is restricted to rodent species such as an obligate monoga- patches of dry deciduous forest with a total mous social and mating System. Pairbonds extension of 20 km x 40 km situated north apparently last until one mate dies. Mates of the town Morondava, along the western defend an exclusive territory throughout

coast of Madagascar. The whole area is sub- the year (for more details see Sommer ject to slash and burn agriculture and com- 1996; 1997; 1998; 2000; Sommer and Tichy mercial logging (Genini 1996; Goodman 1999). One critical component to under- and Rakotondravony 1996). Until recently, stand the population dynamics of an endan-

the Information on H. antimena was limited gered species is its reproductive ecology to anecdotal information (Petter 1972; (for reviews on the behaviour-conservation Starck 1974) and preliminary data from a Interface see Sutherland 1998; Caro

nine-week field study by Cook et al. (1991). 1999). The aim of this study therefore was H. antimena was reported to be strictly noc- to investigate length of the reproductive turnal, to live in long deep burrows and to period, reproductive rate, and offspring move by jumping and running. It was sug- growth of the endangered H. antimena in gested that the rodent lives in social units, its natural habitat. probably consisting of a pair plus their off- Field studies were carried out in the spring. The most surprising information for 12 500 ha forestry concession of the Centre

a rodent species was that it produces only a de Formation Professionnelle Forestiere de Single offspring per year. Most rodent spe- Morondava (C.F.P.F.) in the Kirindy Forest cies are characterised by large litter sizes. (20°03'S 44°39'E) at the research Station

1616-5047/01/66/02-111 $ 15.00/0. © Biodiversity Heritage Library, http://www.biodiversitylibrary.org/

112 Simone Sommer

of the German Primate Center (DPZ, Göt- at end of March (24th March) with a body tingen, Germany). A detailed description mass of around 250 g. of the area is given in Ganzhorn and Sorg In contrast to the anecdotal Information on (1996). Field work took place between Oc- the reproductive rate, the capture/recapture tober 1992 and January 1993, February and studies indicated that not always a male and April 1994, April and June 1995, Novem- female couple was accompanied by a single ber and December 1995 and April and offspring. One single offspring was present June 1996. In a 100 ha study area, all exist- in 60 cases out of 78 investigated family ing burrow Systems were known and were Units but in 11 cases two offspring of the regularly monitored and classified as active present reproductive period lived together or inactive. Capture/recapture studies were in a burrow System with their assumed par- carried at least once during each field peri- ents. The sex ratio of offspring was ba- od. Tomahawk live traps (51x19x19 cm, lanced. Tomahawk, Wisconsin) were set in front of To answer the question whether this can be the burrow holes before the nocturnal ac- explained by the birth of twins or by two tivity period of the started and checked consecutive litters per reproductive period, at least once every hour after sunset until the body mass of offspring which were born the entered the traps. Captured an- during one reproductive period in the same imals were anaesthetised for 10-15 min the burrow were compared (Table 1). Only next morning with an intramuscular injec- data were included in this analysis where tion of 0.1 to 0.25 ml ketamine hydrochlor- all offspring of a pair could be weighed ide (100 mg/ml), sexed, weighed, and meas- within two days. The mean difference in ured. 157 animals from 30 active burrows body mass of offspring trapped in the same have been marked individually with a pas- burrow was 368 ± 89 g (n = 6). In one case sive integrated transponder (Trovan, Rö- (Dec 1992, Tab. 1) two offspring of about merberg, Germany) since the beginning of the same body mass (370 g, 395 g) were the field studies in October 1992. The rats trapped at the same time which were as- were released during their normal activity sumed to be born in the same htter. The period in the evening in front of their bur- data suggest that H. antimena can have two rows. The Statistical tests were performed Single offspring born consecutively during with SPSS (1997). one reproductive period but also twins The study indicated that the reproduction might occur in natural populations. The re- of H. antimena is seasonal and takes place productive rate per couple was calculated during the rainy season (Dec-March). The from trapping results after the reproductive smallest, early born offspring was observed period and was 1.5 offspring in 1994, 1.5 in at the beginning of December (8th Dec) 1995 and 1.1 in 1996. The average number with a body mass of about 200 g and the of marked offspring per pair and year was smallest, late born offspring was observed 1.4. This might be an underestimation as

Table 1. Body mass (g) of offspring which were born during one reproductive period in the same burrow

Trapping date 1. Offspring 2. Offspring Difference ConcLusion

10. 12. 92 395 370 25 twins 24. 03. 94 780 330 450 consecutive htters 25. 03. 94 980 730 250 consecutive h'tters 27. 03. 94 595 250 345 consecutive litters 27.-28. 03. 94 1175 700 475 consecutive litters 01.-02. 06. 95 1040 850 290 consecutive Litters 06. 05. 95 795 400 395 consecutive Litters © Biodiversity Heritage Library, http://www.biodiversitylibrary.org/

Reproductive ecoLogy of Hypogeomys antimena 113

1100

1000

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(/) 600

500 ü o 400 ca 300

200

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March April May June a) Month 1100

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500 ö o 400

300

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Fig. 1. Body mass of all offspring trapped between March and June. Early born offspring are symbolised by trian- gles, late born offspring by drcLes. a: male offspring, b: female offspring. Details on the linear regression lines are given in the text. © Biodiversity Heritage Library, http://www.biodiversitylibrary.org/

114 Simone Sommer

offspring spend the first 4-6 weeks of their Acknowledgements life in the burrow and regularly leave it and can be trapped after another 4 weeks. The studies are supported by the "Commission The reason that to date Hypogeomys was Tripartite" of the Malagasy Government, the La- boratoire de Primatologie et des Vertebres de reported to have only one single offspring rUniversite d'Antananarivo, the Ministere pour per year (Petter 1972; Starck 1974; Cook la Production Animale et des Eaux et Forets, the et al. 1991), might be due to a high offspring Centre de Formation Professionnelle Forestiere mortahty rate. Radiotracking and capture/ de Morondava. J. Ganzhorn, B. Rakotosamima- recapture studies revealed a mean offspring NANA, R. Rasglgarison, L. Razafimanantsoa, mortahty of more than 50% (Sommer WWF International WWF Madagascar, and the 2000). German Research Foundation (So, 428/1-1). In Order to investigate the body mass de- velopment of early and late born offspring of consecutive htters born during one re- productive period and possible sex specific References differences, the body mass of all offspring trapped between March and June were Caro. T. (1999): The behaviour-conservation in- analysed (Fig. mass develop- 1). The body terface. Trends Ecol. Evol. 14, 366-369. late ment of early and born female off- Cook. J. M.: Trevelyan, R.; Walls, S. S.; Hatch- spring and late born male offspring can be ER. M.; Rakotondraparany, F. (1991): The described by a significant linear regression ecology of Hypogeomys antimena, an ende-

(female offspring: early born: R~ = 0.46, mic Madagascan rodent. J. Zool. (London) p = 0.002, late born: R- = 0.74, p - 0.003; 224. 191-200. Ganzhorn, J. U.; Sorg. J-P. (1996): Ecology and male offspring: early born: R~ = 0.09, n. s., Economy of a Tropical Dry Forest in Mada- late born: R- = 0.53, p= O.Ol). The present gascar. Göttingen: Primate Report 46-1. data do not indicate that male and female Genini. M. (1996). Deforestation. In: Ecology offspring differ in the development of their and Economy of a Tropical Dry Forest in body mass (ANOVA: early born: Fi 28 = Madagascar: Ed. by J. U. Ganzhgrn and 2.7, n. s., late born: F1.20 = 0.75, n. s.). The J.-P Sorg. Göttingen: Primate Report 46-1, difference of body mass of early and late 49-55. born offspring during one reproductive per- Goodman, S. M.; Rakotondravgny, D. (1996): iod decreases with increasing age in their The Holocene distribution of Hypogeomys first year of life. At the end of the dry sea- (Rodentia: : Nesomyinae) on Mada- son (Nov/Dec), female offspring weighed gascar: In: Biogeographie de Madagascar. Ed. by W R. LourenJo. Paris: Ed. TORSTOM. 866 ± 177 g (n = 11) and male offspring Pp. 283-293. 863 ± 99 g (n = 5) (t-test: n.s.). Also the Hasler. J. F. (1975): A review of reproduction analyses of other body measurements and sexual maturation in the Microtine ro- (body-, tail-, ear-, hindfoot-, length, head dents. Biologist 57, 52-86. and head width) did not show any age- Petter, F. (1972): The . In: Biogeography dependent differences in male and female and Ecology of Madagascar. Ed. by R. Bat- offspring (Sommer 1998). tistini and G. Richard-Vindard. Den Haag: Although the study indicated that H. anti- W. Junk. Pp. 661-665. mena can have more offspring per couple Sommer, S. (1996): Ecology and social structure of antimena. an endemic rodent of and year than suggested previously, the re- Hypogeomys the dry deciduous forest in western Madagas- productive rate is stih very low. The survi- car. In: Biogeographie de Madagascar. Ed. val prospects of this endangered Speeles is by W. R. Lourenco. Paris: Ed. TORSTOM. critical due to changing environmental and Pp. 295-302. ecological conditions as a consequence of Sommer. S. (1997): Monogamy in Hypogeomys the increasing human impact on the re- amimena, an endemic rodent of the deciduous maining habitat (Sommer and Hommen dry forest in western Madagascar. J. Zool. 2000). (London) 241. 301-314. © Biodiversity Heritage Library, http://www.biodiversitylibrary.org/

Reproductive ecoLogy of Hypogeomys antimena 115

Sommer, S. (1998): Populationsökologie und -ge- SPSS (1997): SPSS Base 7.5 for Windows User's netik von Hypogeomys antimena, einer ende- Guide. Version 7.5 for Windows. Chicago: mischen Nagerart im Trockenwald Westma- SPSS Inc. dagaskars. Diss. thesis, Universität Tübingen. Starck, D. (1974): Die Säugetiere Madagaskars,

Sommer, S. (2000): Sex specific predation rates on ihre Lebensräume und ihre Geschichte. Wies- a monogamous rat {Hypogeomys antimena, baden: Franz Steiner Verlag GmbH.

Nesomyinae) by top predators in the tropical SuTHERLAND, W. J. (1998): The importance of be- dry forest of Madagascar. Behaviour haviour in conservation biology. Anim. Be- 56, 1087-1094. hav. 56, 801-810.

Sommer, S.; Kommen, U. (2000): Modelling the ef- fects of life history traits and changing ecolo- gical conditions on the population dynamics and persistence of the endangered Malagasy giant jumping rat {Hypogeomys antimena).

Anim. Conserv. 4, 333-343.

Sommer, S.; Tichy, H. (1999): MHC-Class II poly- Author's address: morphism and paternity in the monogamous Dr. Simone Sommer, Zoologisches Institut und Hypogeomys antimena, the endangered, Museum, Universität Hamburg. Martin-Luther- largest endemic Malagasy rodent. Mol. Ecol. King-Platz 3, D-20146 Hamburg, (email:

8, 1259-1272. [email protected]).