LAND: Partial migration of red deer and tick distribution at the altitudinal colonization border (TickDeer)

The overall objective of the project "TickDeer" is to understand the importance of red deer migration for ticks and vice versa in areas near the elevational distribution limit. (WP1) Comprehensive data on tick distribution (> 15,000) in the landscape has formed the basis for the PhD degree of Lars Qviller (delivered, defense scheduled 14. Nov. 2014); both spring and autumn flagging for ticks in Sogn & Fjordane (6 years, 2009-14) and in Møre & Romsdal (3 years, 2011-13). It is less ticks in the terrain with increasing elevation and farther away from the coast, and thus less ticks in upland areas of summer migratory deer compared with winter areas and all year areas for stationary animals. The tick has little ability to move, and is spread mainly by host animals. We found more ticks in the core areas of deer in May, ie the increased presence of deer influenced the amount of ticks locally. (WP2) Analysis of ticks load based on counts ears from GPS-collared animals (n=49) is consistent with this work. The deer that migrated far from the lowland winter range to upland summer range had lower tick loads in the fall. Tick load was also higher in areas with a high population density of red deer. Counts of all life stages of ticks on 33 full deerskin showed that the different life stages preferred different areas of the deer; larvae attached to legs and ears, nymphs dominated the ears, while adult ticks largely attached to the groin and neck region. Such a pattern limits the possibility of infection from tick to tick ("co-feeding transmission cycles"). (WP3) We use a DNA-based (PCR) method to detect the prevalence of Anaplasma (causing tick-borne fever in sheep) and Borrelia (causing Lyme borreliosis in humans) in ticks (n = 5636). A key point for management is to know the total impact of deer on the risk of Lyme borreliosis. We are currently finalizing a synthesis that looks at the relationship between 1) tick amplification, 2) pathogen dilution, and 3) the disease risk as a function of the density of deer based on data for the entire period.

We propose to establish a multidisciplinary project to understand the functional significance of red deer migration for an invasive species, the tick, and vice versa at the altitudinal colonization border. The red deer are currently regarded a keystone he rbivore along the west coast of Norway. Alongside this increase in deer density, it is a common perception that the ticks increase in abundance and distribution. The role of animal space use for tick distribution are less well understood. Seasonal migrati on by red deer may potentially play a key role for tick distribution. Equally true, the role of parasites for partial migration pattern in large herbivores have been largely ignored. Ticks can carry and transmit agents of human (Borrelia spp.) and animal disease (Anaplasma spp.), and understanding the role of red deer density and space use for tick density and disease prevalence can provide a key to mitigation efforts. We aim to accomplish such an understanding by a hierarchical, nested sampling design f acilitated by the access to a large number of GPS-marked individuals of red deer (>200) with known migration tactics. This will allow us to (WP1) quantify the distribution of ticks in landscapes along the west coast of Norway relative to migration, local density, and fine-scale space use of red deer as well as relative to habitat. We hypothesize that spring migration by red deer may allow (re)colonization of higher altitude areas, for which ticks are not able to persist either year round or in specific ha rsh years. In WP2, we estimate tick load from ears of GPS-marked animals with known migration tactics and body mass, enabling a study of the relationship between tick load and migratory behavior and performance. In WP3, we link disease in ticks to migrato ry behavior and performance of red deer. This will give important insight into distribution of ticks and a potential role of red deer to serve as vector of ticks and their diseases by seasonal migration.