Invasive animal risk assessment Biosecurity Queensland Agriculture Fisheries and Department of Camel Camelus dromedarius Gina Paroz First published 2008 Updated 2016 © State of Queensland, 2016. The Queensland Government supports and encourages the dissemination and exchange of its information. The copyright in this publication is licensed under a Creative Commons Attribution 3.0 Australia (CC BY) licence. You must keep intact the copyright notice and attribute the State of Queensland as the source of the publication. Note: Some content in this publication may have different licence terms as indicated. For more information on this licence visit http://creativecommons.org/licenses/ by/3.0/au/deed.en" http://creativecommons.org/licenses/by/3.0/au/deed.en Invasive animal risk assessment: Camel Camelus dromedarius 2 Contents Introduction 4 Identity and taxonomy 4 Description 4 Biology 4 Life history 4 Social organisation 5 Diet, thermoregulation and water requirements 5 Preferred habitat 5 Predators and diseases 5 Distribution in Queensland 6 History of introduction 6 Distribution and abundance in Australia 6 Distribution and abundance overseas 8 Management 8 Current and potential impact in Australia 8 Current and potential benefits in Australia 9 Impact overseas 10 Quantitative assessment 12 Introduction 12 Potential distribution 12 Establishment risk 12 Impact and feasibility of control 12 References 12 Appendices 14 Appendix 1. Quantitative risk assessment of pests in Queensland 14 Appendix 2. Potential distribution—CLIMATE parameters 18 Appendix 3. Establishment risk 19 Appendix 4. Impact and feasibility of control 22 Invasive animal risk assessment: Camel Camelus dromedarius 3 Introduction Identity and taxonomy Species: Camelus dromedarius Common names: Camel, dromedary, Arabian camel Family: Camelidae Related species: C. bactrianus (Bactrian camel), Lama glama (llama), L. guanicoe (guanicoe), L. pacos (alpaca) and Vicugna vicugna (vicuña) (Huffman 2004, 2005). Description The key diagnostic features of the camel are body length (300 cm), shoulder height (180–210 cm), tail length (50 cm) and weight (600–1000 kg) (Huffman 2004). Camels have a smooth coat that is beige to light brown, with the undersides slightly lighter. Their legs are long and slender, often with calloused knees, developed from where they touch the ground when the animal is lying down. Though often called the one-humped camel, the dromedary has two humps used for energy storage in the form of fat. The under-developed anterior hump sits over the shoulders and the large rear hump is found in the centre of the back. The upper lip is deeply split and the nostrils can be closed. The camel has long eyelashes to help to keep sand out of its eyes. The two broad toes on the feet are able to spread widely as an adaptation to walking on sand (Huffman 2004). Biology Life history Gestation period: 12–13 months Young per birth: 1 Birth interval: 18–24 months Weaning: 1–2 years Sexual maturity: Females 3–4 years; males 5–6 years Sexual activity: Up to 30 years Lifespan: Up to 50 years (DEH 2004; Huffman 2004). Camel populations have a relatively low maximum rate of increase of around 10% per annum (Edwards et al. 2004) due to a relatively high rate of adult survival and low fecundity. This is typical of large mammals, as is variable juvenile survival (Gaillard et al. 1998). Invasive animal risk assessment: Camel Camelus dromedarius 4 Social organisation Feral camels live in three main types of non-territorial groups: year-round groups of bulls (males), summer groups of cows (females) and calves, and winter breeding groups that include a mature bull and several cows with calves. Old bulls tend to be solitary (DEH 2004). Herds average 11 individuals but larger herds of up to several hundred animals may form in summer or during droughts when groups congregate (DEH 2004; Huffman 2004). In the breeding season, from May to October, single males defend a group of 20 or more cows against advances from other males. Large males engage in ritualised displays that may lead to serious fights. Diet, thermoregulation and water requirements As well as grazing on grass, feral camels browse on vegetation as high as 3.5 m above the ground. They eat a wide range of plant material, including fresh grass and shrubs, preferring roughage to pasture that has introduced grasses or has been fertilised. Camels have a high requirement for salt and they eat salty plants, even devouring thorny, bitter or toxic species that other herbivores avoid. At times when forage is green and moist, feral camels gain all the water they need from their food and do not require drinking water (DEH 2004). Camels are renowned for their ability to survive in hot desert conditions without water for long periods. They have a flexible ‘thermostat’ and will not start sweating until their body temperature reaches 42 oC. Internal body heating mechanisms start when their internal temperature drops below 34 oC. Besides saving energy, this physiological adaptation allows the camel to ‘store’ coolness in preparation for the next day. On hot days, camels will rest together in closely packed groups, which considerably reduces the heat reflecting off of the ground (Huffman 2004). Camels can glean much of their water requirements from desert vegetation and can survive after losing over 40% of their bodyweight in water. If water, whether fresh or brackish, is available in summer, camels will drink regularly and at dawn. In extreme drought camels need access to waterholes, with a dehydrated camel able to drink 200 L in three minutes. The camel’s hump is mostly fat and provides a store of energy rather than water (Huffman 2004). Preferred habitat Feral camels are highly mobile and move over areas up to 5000 km2 (Grigg et al. 1995; Edwards et al. 2001). They wander widely according to conditions, sometimes covering 70 km in a day. In summer, they are usually found in bushland and sandplain country that offers food and shelter from the sun, but in winter they move to salt lakes and salt marshes (DEH 2004). Dörges and Heucke (2003) report that in central Australia, camels feed on more than 80% of the available plant species. Predators and diseases There are no known predators of camels (Huffman 2004). In Australia, it is possible that dingoes or wild dogs take young animals. Camels are susceptible to tuberculosis and brucellosis. Invasive animal risk assessment: Camel Camelus dromedarius 5 Distribution in Queensland History of introduction Camels were first brought into Australia in small numbers in the 1840s (McKnight 1969). Subsequently, demand for draught and transport camels increased and 10 000–20 000 camels were imported to supplement those being bred by the late 1880s. However, as motor transport became more widespread, the camel became redundant and many were released or escaped to form the basis of the today’s feral camel population (Siebert & Newman 1989). Distribution and abundance in Australia Camels now have a wide distribution throughout central Australia and Western Australia, northern South Australia and the Northern Territory (Figure 1). Figure 1. Australian distribution of C. dromedarius (Siebert & Newman 1989). In the 1930s and 1940s, herds of up to 200 camels were seen further to the east of western Queensland (Mitchell et al. 1985). McKnight (1969) reported 15 000 to 20 000 feral camels in Australia, with 1500–2000 in Queensland. Mitchell et al. (1985) reported approximately 1000 camels in the far western districts of Queensland, with seasonal variations in water and food supplies controlling total population size. Camels were reported in the south-west corner of the Diamantina Shire, the north-western corner of the Bulloo Shire, the southern corner of the Winton Shire and around the border of the Boulia and Cloncurry Shires (Mitchell et al. 1985), with populations only occurring on the plains in the far western districts. Figure 2 shows a map of the 1985 and 2000 distribution of camels in Queensland. In 2000, a presence and absence survey was conducted and is overlayed with the 1985 data in Figure 2. At this time, camels were reported in Diamantina, Boulia, Mount Isa, Cloncurry, McKinlay, Richmond and Flinders Shires. The distribution of camels observed in 2000 suggests a range expansion since 1985. However, it is important to note that this information only represents the presence of camels in the shire, and not the distribution within the shire. Invasive animal risk assessment: Camel Camelus dromedarius 6 Figure 2. Queensland distribution of C. dromedarius In 2003, a total of 80 camels were being held in captivity under five declared pest permits in Queensland (Danielle Butcher 2005, pers. comm.). However, this number probably underestimates the number of camels held in Queensland. Edwards et al. (2004) reported a minimum estimate of 80 500 camels in the Northern Territory in 2001, with an overall population throughout Australia of 300 000. They observed a population increase close to the maximum rate of ~10% per year between aerial surveys in 1991 and 2001. This equates to an approximate doubling in population size every eight years (Edwards et al. 2004). Although the population cannot maintain this growth indefinitely, there is no indication that a reduction will occur soon (Edwards et al. 2004). Assuming maximum population growth, McKnight’s (1969) estimate of 4500–6000 camels in the Northern Territory would have increased to 72 000–96 000 camels by 1999. In Queensland, the population estimates of McKnight (1969), Mitchell et al. (1985) and Edwards et al. (2004) were projected to estimate a 2005 Queensland feral camel population of between 24 000 and 32 000. These population estimates are significantly less than the 50 000 camels in Queensland suggested by Warfield and Tume (2000). Invasive animal risk assessment: Camel Camelus dromedarius 7 Distribution and abundance overseas Originally confined to Arabia, the domestic camel now inhabits the deserts of northern and north-eastern Africa, the Middle East and central Asia (Lever 1985).