The effects of deer carcasses on upland food webs

Decomposition and nutrient cycling of organic materials are critical processes that influence the structure and functioning of ecosystems worldwide.

Wild red deer are iconic species in Scotland. They are important for hunting, tourism and provide venison. However, at high densities their grazing impact can be detrimental to some habitats. As a result deer are shot for both sporting reasons and to control the size of the population. Whereas carcasses from natural mortality usually remains on the hill carcasses from shot animals are normally removed and represent a loss of nutrients and energy from the upland food web. There is increasing interest among some stakeholders in leaving some carcasses from culled deer on the hill because:

• of the logistical constraints of extracting carcasses in some areas, and
• interest in the potential ecosystem benefits of leaving carcasses on the hill, because of the role these nutrients may play in enhancing biodiversity.

However, there are practical and strong ethical arguments for ensuring carcasses are removed, used for venison and not wasted.

Aims and objectives

Decomposition and nutrient cycling of organic materials are critical processes that influence the structure and functioning of ecosystems worldwide. However, few studies have quantitatively addressed the decomposition and associated effects of vertebrate carrion. We aim to quantify the environmental effects of leaving deer carcasses in the Scottish uplands.

Hypothesis

Estate management influences the guild of vertebrate carrion feeders present and therefore affects carcass decomposition rates with consequences for how nutrients from the carcass enter the upland food web and the relative importance of vertebrate and invertebrate carrion feeders (Fig.1 ). This project will address two complimentary but independent questions.

1. What are the spatial and temporal effects of deer carcasses on upland terrestrial food webs?
2. How does estate management, for example, predator control, influence the rate of decay, release of nutrients and subsequent effects on upland terrestrial food webs?

Camera trapping data show that a range of animals use carcasses (Fig. 2).

Figure 2: Some of the animals caught by camera traps placed at deer carcasses. (a) red fox, (b) pine martin, (c) golden eagle, and (d) otter.