Charles JK

Gaulton R

Khalid S

Mannion NLM

Pfeifer M

Slik JWF

Wong Sia How J

English

Pure white animals have long been regarded as unusual and prized by hunters. For the first time, we report an incidence of a white lesser mouse deer (Tragulus kanchil), observed by camera trap in Brunei Darussalam. This adult individual was recorded on four separate occasions in the same location. Although the underlying cause of this rare phenotype is undeterminable from camera trap images, the individual does not display the pink eyes commonly characteristic of albinism. It is surprising that this individual has survived to adulthood, as its bright white colouration makes it more vulnerable to predation, as well as a target for hunters. Further study of this individual could reveal insights into how it has survived, and the genetic health of the local population of T. kanchil

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1  A novel white mouse deer observation in Brunei Darussalam Authors: Natasha L. M. Mannion1*; Joseph K. Charles2; Rachel Gaulton3; Jerry Wong Sia How4; Salwa Khalid5; Marion Pfeifer6; J. W. Ferry Slik7 1 – School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom; https://orcid.org/0000-0002-3985-4420 ; n.mannion2@newcastle.ac.uk *- corresponding author 2 - The Mesozoic Explorers Company, No.2 Simpang 398, Jalan Subok, Bandar Seri Begawan BD2717, Brunei Darussalam; https://orcid.org/0000-0001-9284-7820  3 - School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom; https://orcid.org/0000-0002-0706-0298  4 – Kampong Sungai Tilong, Jalan Muara, Bandar Seri Begawan, BC 3315, Brunei Darussalam; https://orcid.org/0009-0001-8950-4840  5 - Institute for Biodiversity and Environmental Research, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam; https://orcid.org/0000-0002-7230-7242 6 - School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom; https://orcid.org/0000-0002-6775-3141  7 - Environmental and Life Sciences, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong, BE1410, Brunei Darussalam; https://orcid.org/0000-0003-3988-7019  Word count: 1,382 Abstract  2  Pure white animals have long been regarded as unusual and prized by hunters. For the first time, we report an incidence of a white lesser mouse deer (Tragulus kanchil), observed by camera trap in Brunei Darussalam. This adult individual was recorded on four separate occasions in the same location. Although the underlying cause of this rare phenotype is undeterminable from camera trap images, the individual does not display the pink eyes commonly characteristic of albinism. It is surprising that this individual has survived to adulthood, as its bright white colouration makes it more vulnerable to predation, as well as a target for hunters. Further study of this individual could reveal insights into how it has survived, and the genetic health of the local population of T. kanchil.  Keywords: Tragulus, mouse deer, camera trapping, leucism, albinism, Borneo,  Mouse deer are small, even-toed ungulates of the genus Tragulus, found throughout Southeast Asia.  There are two species of mouse deer on Borneo, the greater mouse deer (Tragulus napu) and the lesser mouse deer (Tragulus kanchil), which are both brown with white and brown markings around the chest and neck (Phillipps and Phillipps 2016).  We recorded an observation of a white mouse deer as part of a wider camera trapping study assessing the impacts of infrastructure expansion on mammal biodiversity in the Temburong district of Brunei Darussalam. Although some records of white mouse deer have been reported both from the wild and in captivity  (Bond, Zoological Society of London, and Bridgeman Images 1926; Borneo Post Online 2015; Jumpei 2006), this appears to be the first record of a white mouse deer in the wild on Borneo.  This study was conducted across Temburong, Brunei Darussalam. Temburong is a rural and heavily forested district containing over 64,000 hectares of forest reserves, including the large Batu Apoi Forest Reserve (Forestry Department, Brunei Darussalam, personal communication, 29th October 2022). It is an eastern exclave of the rest of the country, and 3  transport links to the three western districts have recently been improved with the construction of the Sultan Haji Omar Ali Saifuddien bridge in 2020. Camera traps were deployed at 66 sites across the region in a study design incorporating different levels of infrastructure pressure and varying distances from the nearest road. Although Temburong features mangroves, peat swamp forests, and kerangas (heath forest), this study focused on mixed dipterocarp forest. The total survey effort for this study was 2264 trapping nights (2152 trapping nights accounting for cameras tampered with after deployment).  The white specimen was observed at one of these camera trap sites. We refrain from including the coordinates or a detailed description of the site due to the specimen’s allure to hunters, who have been known to use information from scientific publications to inform their hunting activities in the region (J. K. Charles, personal communication, 17th May 2022; S. Khalid, personal communication, 17th May 2022). The site was in northern Temburong, in mixed dipterocarp forest which showed some signs of disturbance, over 1 km from the nearest road.  The camera trap used was a Browning Strike Force HD Pro X BTC-5HDPX.The camera was attached to a tree with the sensor approximately 50 cm above the ground, pointed at a 45-degree angle to an apparent game trail. The camera was deployed between 12/04/2022 - 17/05/2022 (35 trap nights). The study design aimed for a 1 km inter-trap distance; in practice the next two closest sites were 878 m and 721 m from this site.  In total, 123 images of a white mouse deer were captured from this site. Due to the lack of previous records of white mouse deer implying its rarity we assume this is the same individual. These comprised of four separate events: 19/04/22, 25/04/22, 28/04/22, and 4  10/05/2022 (Table 1). The specimen appears to be pure white over its body, with pale pink ears, nose, and mouth, and dark eyes (Fig. 1). Using field guides, by comparison with camera trap images of mouse deer from the same site and across the wider study, and in consultation with a local expert, this species was tentatively identified as a lesser mouse deer (Tragulus kanchil) (Phillipps and Phillipps 2016). Although the neck and chest markings, one of the key characteristics used to distinguish between T. kanchil and the similar Tragulus napu, were absent, this individual was determined as being T. kanchil based on comparison with the one other Tragulus record from this site, a pair of T. kanchil presumed to be an adult female and fawn, on 30/04/2022 between 18:15:36 to 18:16:38. This pair was confidently identified by an unbroken white line in its neck markings, smooth fur, and head profile (Fig 2.). This is the first time leucism or albinism has been reported in a wild mouse deer in Brunei Darussalam. Some previous records of white mouse deer have been reported, however we could only find two records captured from the wild (Bond, Zoological Society of London, and Bridgeman Images 1926; Borneo Post Online 2015; Jumpei 2006). These were both captured in Langkawi, Malaysia, the first in 2001 and the second in 2015 (Borneo Post Online 2015). Although we cannot determine for certain whether the individual is albino or leucistic, it appears to have dark eyes. This possibly suggests leucism over albinism, which commonly impacts eye pigmentation resulting in pink or blue eyes. However, as some variants of albinism are not associated with abnormal eye colour, and there are several genes linked to an unusual white phenotype it is not possible to say for certain (Oetting and Adams 2018). The individual’s white colouration is expected to make it more vulnerable to predation by significantly reducing its natural camouflage, and it is surprising that it seems to have reached 5  adult size. We note that all four records of this specimen were obtained during the day. This may reflect T. kanchil’s typically diurnal behaviour (Phillipps and Phillipps 2016). Unpublished data from a wildlife survey carried out in the Sungei Ingei Conservation Forest in the Belait District, Brunei Darussalam supports this, showing that T. kanchil was active between 0600-1900 hrs (2010-2012; J.K. Charles personal communication, 16th March 2023). By contrast T. napu is thought to be more active at night (Phillipps and Phillipps 2016). In the same unpublished data, T. napu showed arrhythmic temporal activity (46.75% of records occurred between 1800-0600 hrs, 53.25% occurred between 0600-1800 hrs) (J.K. Charles personal communication, 16th March 2023). 88.1% of all other Tragulus records from the wider study in which this individual was recorded were at night (defined images being captured using infrared flash due to low light and timestamp). Of the images identified to species level only one T. kanchil record occurred outside of the 0600-1900 hr range, but 67% of these images were captured using the infrared flash (n = 6). 95.9% of T. napu records were also captured using the infrared flash (n = 49). Alternatively, the diurnal behaviour of the white mouse deer could represent a behavioural adaptation to reduce the risk of predation, as its bright colouration would make it more visible to nocturnal predators. Further study of this individual, such as tracking by radio collar, could shed light on its behaviour and how it has evaded predation thus far. In addition to its natural predators, its rare colouration would also increase the specimen’s vulnerability to hunting. White animals are often prized by hunters, and we were warned by local collaborators to be careful when sharing these images and their location as the specimen would be a desirable target (J. K. Charles, personal communication, 17th May 2022; S. Khalid, personal communication, 17th May 2022). Hunting signs such as snares were noted in the area of this camera trap. 6  The white phenotype of this individual may also indicate low genetic diversity in this population of T. kanchil. Albinism has been linked to inbreeding depression in some species, and some cases of leucism have been linked to the expression of recessive genes, which can be more common in inbred populations (Bensch et al. 2000; Flis et al. 2018; Guastalla et al. 2021; Prado-Martinez et al. 2013). For example, low genetic variability could have arisen in this population due to habitat fragmentation leading to lack of connectivity between populations and subsequent genetic isolation. This indicates a general need for further study of Bruneian mammal populations, and the possible impacts of habitat fragmentation and hunting.  Acknowledgements Many thanks to Sawai, Rebekah Puttick, Bethany Holdsworth, and Lucy Eberhardt for field assistance throughout the project. We would like to thank the Brunei Forestry Department, Ministry of Primary Resources for granting a forest entry permit (JPH/UND/17 dated 12 October 2021) to conduct research. We are grateful for the support of the Institute for Biodiversity and Environmental Research at Universiti Brunei Darussalam. Author contributions Natasha Mannion, Rachel Gaulton, Salwa Khalid, Marion Pfeifer, and Ferry Slik contributed to the study conception and design. Natasha Mannion and Jerry Wong conducted data collection. Joseph Charles contributed to species identification. Material preparation was performed by Natasha Mannion. The first draft of the manuscript was written by Natasha Mannion and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Research funding 7  The research leading to this finding received funding from the IAPETUS2 Doctoral Training Partnership (NERC), with additional support by the Newcastle University Faculty of Humanities and Social Sciences, (Pioneer Award 2021), the Newcastle University Faculty of Science, Agriculture and Engineering and Research England, and the Royal Geographical Society with IBG (RGS-IBG Postgraduate Research Award). Competing interests The authors have no competing interests to declare that are relevant to the content of this article. Compliance with ethical standards The studies have been approved by research ethics committees at both Newcastle University (Animal Welfare and Ethical Review Body; ID 897 16/09/2021) and Universiti Brunei Darussalam (FOS Research Ethics Committee, Universiti Brunei Darussalam; UBD/FOS/E2(g) 10/07/2021).   References Bensch, Staffan, Bengt Hansson, Dennis Hasselquist, and Bo Nielsen. 2000. ‘Partial Albinism in a Semi-Isolated Population of Great Reed Warblers’. Hereditas 133(2): 167–70. Bond, Frederick William, Zoological Society of London, and Bridgeman Images. 1926. ‘An Albino Javan Chevrotain/Java Mouse-Deer Eating from a Bowl at London Zoo in 1926 (b/w Photo)’. Bridgeman Images. https://www.bridgemanimages.com/en/noartistknown/title/notechnique/asset/3587744 (November 21, 2022). 8  Borneo Post Online. 2015. ‘Captured Rare White Mousedeer Draws Visitors to Villager’s House in Langkawi’. Borneo Post Online. https://www.theborneopost.com/2015/02/26/captured-rare-white-mousedeer-draws-visitors-to-villagers-house-in-langkawi/ (November 21, 2022). Flis, Marian, Eugeniusz R. Grela, Dariusz Gugała, and Bogusław Rataj. 2018. ‘The occurrence of albinism in roe deer: A case study’. Medycyna Weterynaryjna 74(1): 6036–2018. Guastalla, Michelle Granato et al. 2021. ‘The Mysterious White Deer: Anomalous Coloring in Different Neotropical Deer’. Mammalian Biology 101(5): 665–73. Jumpei, Kimura. 2006. Participating the 2nd Symposium on Asian Zoo and Wildlife Medicine and Collaborative Research Work in Yangon Zoological Gardens. Kyoto University. http://www.pri.kyoto-u.ac.jp/hope/reports/18-055.html (November 21, 2022). Oetting, William S., and David Adams. 2018. ‘Albinism: Genetics’. eLS , John Wiley and Sons, Ltd (Ed.). https://onlinelibrary.wiley.com/doi/10.1002/9780470015902.a0006081.pub3 (November 21, 2022). Phillipps, Quentin, and Karen Phillipps. 2016. Phillipps’ Field Guide to the Mammals of Borneo and Their Ecology. Princeton: Princeton University Press. Prado-Martinez, Javier et al. 2013. ‘The Genome Sequencing of an Albino Western Lowland Gorilla Reveals Inbreeding in the Wild’. BMC Genomics 14(1): 363.    9  Figure captions Fig. 1 Four images of a white mouse deer specimen captured by camera trap in the Temburong district, Brunei Darussalam. The images were captured on the following dates: a) 19/04/22, b) 25/04/22, c) 28/04/22, d) 10/05/2022  Fig. 2 An image of a pair of Tragulus kanchil (lesser mouse deer), presumed to be an adult female and fawn, captured by camera trap in the Temburong district, Brunei Darussalam, on 30/04/2022.  10                11  Table 1. Summary of four camera trap capture events of a white specimen of Tragulus kanchil. Event Number of images Date and time of first image Date and time of last image 1 61 19/04/22 10:38:51 19/04/22 10:39:22 2 28 25/04/22 07:55:28 25/04/22 07:55:48 3 37 28/04/22 07:07:28 28/04/22 07:07:49 4 21 10/05/2022 09:09:32 10/05/2022 09:09:43  

A novel white mouse deer observation in Brunei Darussalam

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A novel white mouse deer observation in Brunei Darussalam

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