Journal of Arid Environments 141 (2017) 7e15 Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv Burrow characteristics and its importance in occupancy of burrow dwelling vertebrates in Semiarid area of Keoladeo National Park, Rajasthan, India * Aditi Mukherjee a, b, Rajan Pilakandy a, Honnavalli Nagaraj Kumara a, , Shirish S. Manchi a, Subramanian Bhupathy a, 1 a Salim Ali Centre for Ornithology and Natural History, Anaikatty (Post), Coimbatore, 641 108, Tamil Nadu, India b Manipal University manipal.edu, Madhav Nagar, Manipal, 576 104, Karnataka, India article info abstract Article history: Burrows are engineered shelters providing crucial refuge and protection against temperature extremes, Received 29 June 2016 fire and predation. Understanding the ecological role of them in terms of providing habitats to other Received in revised form animals is very significant. Burrowing animal assemblages occur in almost all landscapes, particularly in 23 December 2016 arid and semi-arid habitats. The present work was carried out to understand external and internal Accepted 9 February 2017 burrow features and to identify the factors determining the animal assemblage. A total of 44 burrow systems were located in Keoladeo National Park, India. External burrow characteristics such as: number of openings, inter-opening distances, size and opening orientation were collected. The internal archi- Keywords: ¼ Burrow architecture tecture (n 9) of the burrow systems was studied using a burrow video camera. The internal charac- Burrow co-occupancy teristics such as: dimensions of tunnels and chambers, total length, number of branches, and distance Burrow video camera between chambers were collected. Degree of convolution and Reichman's index were used to determine Camera trap the complexity and linearity. Camera traps and a burrow video camera were used to determine the Semi-arid presence of animals dwelling inside. The burrow systems had a looping structure with a mean total Keoladeo National Park length of 13.33 ± 6.51 m. Burrow systems were co-occupied by four vertebrate species; Indian crested porcupine, golden jackal, leaf-nosed bat and Indian rock python. All the animals except porcupines, were observed to occupy burrows based on specific burrow characters, wherein jackals occupied burrows with larger chambers, pythons occurred in smaller compact chambers and bats occupied burrows with fewer branching and openings. The occupancy of Indian crested porcupine and gecko did not show any sig- nificant correlation with burrow characters. Occupancy of jackal was positively correlated (r ¼ 0.72, P < 0.05) and python was negatively correlated (r ¼0.82, P < 0.01) with mean chamber height. Bats showed a significant negative correlation with number of branches (r ¼0.69, P < 0.05) and number of openings (r ¼0.85, P < 0.01). © 2017 Elsevier Ltd. All rights reserved. 1. Introduction be crucial micro-refuge (Kinlaw, 1999), especially in arid and semi- arid regions providing protection against temperature extremes, Most animals use some kind of refuge either daily or seasonally. fire and predation (Alkon and Saltz, 1988; Campbell and Clark, Burrows in terrestrial habitats are one of the oldest forms of 1981; Reichman and Smith, 1990). Three major categories of bur- engineered shelters (Voorhies, 1974) reported as early as the rowing vertebrates have been identified by Kinlaw (1999) and Carboniferous Period (Olsen and Bolles, 1975). Burrows appear to have been broadly classified into: ‘primary excavators’ for whom digging burrows is an inevitable part of their life-cycle; ‘secondary modifiers’ that occupy and further transform the burrows of pri- ‘ ’ * Corresponding author. mary excavators and, the third category of simple dwellers that E-mail addresses: [email protected] (A. Mukherjee), rajandudu@ take advantage of the existence of burrows and occupy them. gmail.com (R. Pilakandy), [email protected] (H.N. Kumara), ediblenest@ Burrowing vertebrates are hence potential ecosystem engineers gmail.com (S.S. Manchi). (Jones et al., 1994) with the capability of modifying habitats and 1 Deceased 28 April 2014. http://dx.doi.org/10.1016/j.jaridenv.2017.02.003 0140-1963/© 2017 Elsevier Ltd. All rights reserved. 8 A. Mukherjee et al. / Journal of Arid Environments 141 (2017) 7e15 directly or indirectly regulating resource availability for other taxa adapted to semi-arid conditions, such as Prosopis juliflora and species (Hansell, 1993; Jones et al., 1994; Lynn and Delting, 2008). Salvadora sp., are common in the area. The total area of KNP is They are known to have positive and negative effects on the 29 km2, including about 8.5 km2 of wetland. The terrestrial habitat ecosystem, species richness and abundance at small scales contributes three times the area of the park's wetland harbouring a (Hansell, 1993), but an overall positive effect at larger scales in wide variety of resident migratory birds and provides a favourable ecological and evolutionary time and space (Jones et al., 1997). Of habitat for a good number of reptiles and mammals (Vijayan, 1991). all burrowing vertebrates, mammals have been identified as pri- mary burrow excavators (Kinlaw, 1999) constructing complex 2.2. Field methods burrow systems. In arid and semi-arid regions, rodents form the major group of burrowing mammals with elaborate multi-tier Field surveys were conducted from September 2013 to February burrow systems (Prakash, 1997), which facilitates them to unload 2016. The study area was overlaid with a 25 ha grid layer resulting excessive heat due to high mean temperature during summer. in a total of 101 grids on terrestrial area. To locate the burrows, each Burrow inhabitants are even reported to be either in obligate and/ grid (25 ha i.e. 500 Â 500 m) was sub-divided into four or non-obligate commensal associations (Kinlaw, 1999; Kiviat, (250 Â 250 m) sub-grids (Fig. 1), and each sub-grid was system- 1978). Several studies report vertebrate associates in the burrows atically surveyed in a zigzag trail. The geo-coordinates for all the of Orycteropus afer aardvark (20 vertebrate, Smithers, 1971), located burrows were recorded using handheld global positioning Pedetes capensis spring hare (7 vertebrates, Smithers, 1971), Cyn- system. Upon locating the burrows, external burrow characteristics omys spp. prairie dog (64 vertebrates, Campbell and Clark, 1981), were recorded including number of openings in a burrow system, Gopherus agassizii desert tortoise (23 vertebrates, Luckenbach, inter-opening distance, size of openings (in meters), orientation of 1982), Gopherus polyphemus gopher tortoise (60 vertebrates, openings (in cardinal degrees). For recording the internal burrow Jackson and Milstrey, 1989), Dipodomys spp. kangaroo rat (14 characteristics, nine burrow systems were randomly selected. A species of reptiles, Hawkins and Nicoletto, 1992)andMeles meles customised burrow video camera (BVC) was used attached with European badger (Eight mammal species, Mori et al., 2014). In metered cable to determine the internal length and other burrow India, studies on burrow dwelling animals and their activities are characteristics. To determine the internal dimensions of tunnels scanty. Goyal and Ghosh (1993) excavated and examined seasonal and chambers (Fig. 2), photographs were digitised with a reference changes in burrow structure of the Indian gerbil Tatera indica and scale (here the BVC was the measuring unit); at least five obser- Indian desert gerbil Meriones hurrianae in the Thar Desert and vations were taken for each chamber and tunnels for higher accu- found that burrow systems of Tatera indica were of a simple ‘Y’ racy. As the BVC was manoeuvred inside, the internal structure of shaped type with one or two surface openings and with a the burrow was graphically drawn along with recording internal maximum depth of 35 cm in winter to 45e50 cm in summer, dimensions including number of branches, number of chambers whereas burrow systems of Meriones hurrianae were complicated and internal surface types. The internal surface types (Fig. 3)were and extensive with numerous openings and with no significant broadly characterised into three types, namely (a) flat undulating seasonal change in burrow depth. Fitzwater and Prakash (2009) surface with rigid soil, (b) flat surface with loose soil and (c) excavated the burrows of Indian desert gerbil Meriones hurrianae irregular surface with loose soil and gravel. The total above-ground and reported the behaviour and home range of this species in area covered by the burrow system was measured from the graphs Jaisalmer, Bikaner and Palsana districts of Rajasthan. The gerbil using the minimum convex-polygon method (Southwood, 1978). burrows were of three types: superficial burrows up to 3 m long The internal length and total above ground area of the burrow and 5e10 cm deep, shallow burrows up to 25 cm deep which systems were recorded to measure the complexity and configura- usually led to deep burrows with maximum depth reported by tion of the burrow system. To record the presence of burrowing Bikaner (110 cm), followed by Palsana (108 cm) and Jaisalmer vertebrates, camera traps (Boskon Guard Scouting IR Camera, BG- (65 cm). Bhupathy and Ramesh (2010) reported several species of 520 series) were continuously deployed in front of the burrows vertebrates inhabiting Indian crested porcupine Hystrix indica and a burrow video camera were used once in five days. burrows in Keoladeo National Park