Rodent Seed Predation!
Rodent Seed Predation!
Castanopsis concinna (Fagaceae) is a Class III protected tree species in China. It is classified as "Endangered" in the China Plant Red Data Book (Fu, 1992). In Hong Kong, it was recorded by Zhuang et al (1997) at only three sites and was considered rare, although Fellowes (1992) also found it in the Lion Rock Country Park in addition to the old records of this species at 5 other locations. There are about 50 trees spreading along the Middle Gap Road, Hong Kong Island. I went there on 8th December 1998 and collected about 900 seeds on the forest floor of the biggest patch of C. concinna for the Native Tree Nursery of KFBG. Seeds had just started falling on that day. I then went back to the same forest patch on 4th February trying to collect more seeds and a 15-minute search on the forest floor found no intact seeds. Instead, the forest floor was full of broken seed coats - an apparent sign of rodent seed predation.
Since the germination rate of this species in normal nursery conditions is fairly good (43% in the batch collected in January 1998), the near-absence of young seedlings on the forest floor appears to be attributable to seed predation by forest rodents (such as Sladen's rat Rattus sikkimensis or the chestnut spiny rat Niviventer fulvescens). This may explain why a recent (September 1998) study of mycorrhizae undertaken by the HK Polytechnic University turned up only three young C. concinna seedlings in the forest patch in question.
Interestingly, there are a lot of Cyclobalanopsis myrsinifolia, one of the common Fagaceae species in Hong Kong, at the forest patch. It fruits earlier than C. concinna but for a much longer period (from October to the next February). C. myrsinifolia does not seem to suffer to the same extent from rodent seed predation at this site, as the forest floor is full of seedlings of various ages. C. myrsinifolia was, however, found to be eaten by rodents in my earlier study on tree seed predation in Hong Kong (Hau, 1997). The difference may be due to the fact that C. myrsinifolia fruits in very large quantities every year (pers. obs. since 1994) and thus avoids the devastating effect of seed predation by predator satiation.
BILLY HAU
References
Hau, C.H., 1997. Tree seed predation on degraded hillsides in Hong Kong. Forest Ecology and Management, 99:215-221.
Fellowes, J.R., 1992. Hong Kong Macaques. Unpublished report to the WWF Hong Kong Projects Committee 164 pp.
Fu Li-guo (Ed.)., 1992. China Plant Red Data Book, Volume 1. Science Press, Beijing. 736pp. (In Chinese).
Zhuang Xueying, Xing Fuwu, and Richard T. Corlett, 1997. The Tree Flora of Hong Kong: Distribution and Conservation Status. Memiors of the Hong Kong Natural History Society, 21:69-126.
P.20-21
Hong Kong's Barking Deer - What is it?
For some time now, a number of local ecologists - Bosco Chan foremost amongst them - have suspected that the resident species of muntjac (or 'barking deer') is too large to be the Chinese muntjac Muntiacus reevesi - the name given in Hill & Phillipps (1981). This somewhat outdated and error-strewn text is still the only field guide available for Hong Kong mammals. The suspicion was fuelled by discussions with Prof. Yuan Xicai at South China Institute of Endangered Animals in Guangzhou, who reported that M. reevesi does not occur in southern Guangdong.
On 1 April 1999, an injured muntjac from Shing Mun was admitted to the rescue centre at KFBG. Unfortunately, the animal had to be euthanised due to complications arising from its wounds (it had been badly mauled by dogs either before or after falling into a catchwater). This has provided KFBG staff a rare opportunity to make a detailed examination of the animal. Initial comparison of body measurements with figures quoted in Corbett & Hill (1992) and Boonsong & McNeely (1988) would indicate that this specimen is probably Muntiacus muntjak (Indian muntjac), a species not previously recognised as resident in Hong Kong. The carcass will be cleaned and preserved for full measurements, and tissue samples have been taken.
The ranges of Muntiacus reevesi and M. muntjak overlap across mainland southern China from Yunnan to Fujian (Corbet & Hill, 1992). M. reevesi extends north through palaearctic China, while M. muntjak has a much more tropical distribution, extending westwards to India and Sri Lanka, and south through Indo-China to Indonesia (Corbet & Hill, 1992, Nowak, 1991). The Indian muntjac is apparently the commonest species of deer in Thailand (Boonsong & Lekagul, 1988). A 1987 study cited by Nowak (1991) estimates that the Chinese populations of M. reevesi and M. muntjak number 650,000 and 140-150,000 respectively.
The Indian muntjac typically feeds on the edges of forests or in abandoned clearings, both as a browser and as a grazer (Boonsong & Lekagul, 1988). Hill & Phillipps (1981) suggest that the characteristic bark of the local species is made only by males during the breeding season. However, it is uncertain when (or if) a distinct breeding season occurs (see Nowak, 1991). At any rate, barking is heard throughout the year in Hong Kong (as a survey of the Wildlife Windows sections of Porcupine! back numbers attests), and is more likely a response by both sexes to predator detection (Nowak, 1991).
On a sad note, the individual admitted to the KFBG rescue centre turned out to be a pregnant female carrying a 200g foetus (now also preserved). We will update as we know more.
GRAHAM REELS & PAUL CROW
References
Boonsong, L. & McNeely, J.A. (1988). Mammals of Thailand -Second Edition. Association for the Conservation of Wildlife, Bangkok. 758 pp.
Corbet, G.B. & Hill, J.E. (1992). The Mammals of the Indomalayan Region. Oxford University Press, Oxford. 488 pp.
Hill, D.S. & Phillipps, K. (1981). Hong Kong Animals. Government Printer, Hong Kong. 281 pp.
Nowak, R.M. (1991). Walker's Mammals of the World - Fifth Edition. Johns Hopkins University Press, Baltimore and London. 1,629 pp.
P.21
Important discovery of Lesser Bamboo Bat roosting site in Hong Kong
The insectivorous bamboo bat (Vespertilionidae: Tylonycteris pachypus) was a newly discovered species for Hong Kong in 1996 (Porcupine! 15:10). Since its discovery I have attempted to locate the roosting site to get an idea of its abundance in Hong Kong. Bamboo that I have investigated over the last two years was apparently not suitable for this species, perhaps due to age and location. However, during a recent visit to a fung shui wood in Ping Che with members of the KFBG Ecological Advisory Group, a colony of this tiny (3.5cm) bat was discovered in a clump of mature spiny bamboo . Michael Lau while searching for amphibians with a torch noticed a small mouse-like face peering out of a vertical lip-shaped hole in a live bamboo trunk.
The bamboo was large with some stalks measuring 15cm in diameter. Once we had identified the roost characteristics we were able to locate several other roosts varying in height from 1 - 3 m up the bamboo, and estimated that about 10 bats using this particular clump. Bats were roosting singly or in pairs between nodes. Often the holes were carpeted with droppings but difficult for any predators to enter. The holes were probably started by carpenter bees and enlarged by the bats. It was interesting to note that the bats were not interested in holes and cracks in dead bamboo - perhaps because of the lack of moisture?
This represents the first roost site discovered locally for this species, making it of high conservation value. The discovery also highlights the importance of mature bamboo groves in Hong Kong, since all bat species are protected and any clump of large bamboos might potentially contain a colony of this bat.
The South China status of this species is uncertain, but it has been recorded in Guangxi, southern Yunnan, southern Guizhou and in Guangzhou.
GARY ADES
P.22
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