Interactions between climate, host refuge use, and tick population dynamics

Abstract

The relationship between Australian sleepy lizard (Tiliqua rugosa) microhabitat use and tick (Amblyomma limbatum) population dynamics was investigated. Over 3 years (2002-2004) between 23 and 50 lizards were radio-tracked up to four times a week to record microhabitat use and each fortnight to determine tick loads. Daily maximum temperature was highly predictive of lizard microhabitat use. In hotter fortnights lizards used larger bushes and burrows for refuge. Peak background tick infestation levels and pulses of attachment coincided with higher ambient temperature. Male ticks attached throughout the year independent of season. Engorged females detached late in spring, summer and autumn, when climate regularly restricted lizards to a few thermally conservative refuges. Peak nymph and larval attachment occurred over summer and into autumn. Climate-dependent timing and type of host refuge use may influence tick population density. In more temperate summers lizards may avoid refuges with potentially high parasite loads.

Refuge sharing network predicts ectoparasite load in a lizard

“…Nevertheless, here, we argue that in the sleepy lizard high node connectivity is more likely to lead to high tick loads. This is consistent with the report that sleepy lizards have increased tick loads after periods of high temperatures when multiple lizards repeatedly share the same cool temperature mammal burrows (Kerr and Bull 2006b). Because burrows are scarce, lizards are generally unable to avoid previously used burrows.…”

“…Engorged ticks normally detach at night in a host refuge. They molt to the next stage and then wait for their next host in that refuge (Petney et al 1983; Chilton and Bull 1993b; Kerr and Bull 2006b). Remaining in lizard refuges increases tick exposure to new hosts and reduces risks of desiccation and predation by ants, the two major threats to off-host tick survival (Bull et al 1988; Chilton and Bull 1993a, b).…”

When the going gets tough: behavioural type-dependent space use in the sleepy lizard changes as the season dries

“…Nevertheless, many of the observed seasonal trends (e.g. stronger positive responses to Refuge rank, Late food, Cover, and distance to the nearest dam during the Late season) agree with simple expectations based on seasonally increasing heat stress and resource deterioration [41]. Resource availability at the neighbourhood spatial-scale was a consistently better predictor of lizard space use than at the local scale, implying spatial decisions are influenced by a larger scale than our single quadrats.…”

“…Since annual plants grow in the spring and then dry out in the summer, leaving increasingly rare patches of food plants for lizards as the season progresses, there is a strong seasonal effect within each year on available food resources [32,39]. This seasonality affects the movements and behaviour of lizards, and shaded refuges (typically large dome-shaped shrubs, fallen trees, or mammal burrows) become important later in the season as lizards seek to avoid high heat stress [39][40][41]. The study area has a dirt road crossing it from east to west, with two building ruins and two seasonal dams that retain water and soil moisture for longer than other parts of the area.…”

Abiotic and Biotic Factors Associated with Tick Population Dynamics on a Mammalian Host: Ixodes hexagonus Infesting Otters, Lutra lutra

“…Together with the elevated humidity produced, such weather conditions may lead to increased abundance of I. hexagonus , as reported for I. ricinus and I. scapularis [17], [19], [20]. This may be related to the weather conditions causing changes in the behaviour of either the parasite or the host thereby altering infestation rates (see [39]). No previous literature was found relating NAO to I. hexagonus .…”