The Olfactory Landscape Concept: A Key Source of Past, Present, and Future Information Driving Animal Movement and Decision-making

Abstract

Odor is everywhere, emitted across the landscape from predators, prey, decaying carcasses, conspecifics, vegetation, surface water, and smoke. Many animals exploit odor to find food, avoid threats, and attract or judge potential mates. Here, we focus on odor in terrestrial ecosystems to introduce the concept of an olfactory landscape: real-time dynamic olfactory contours reflecting the patchy distribution of resources and risks, providing a key source of information used by many animals in their movement and decision-making. Incorporating the olfactory landscape into current frameworks of movement ecology and animal behavior will provide a mechanistic link to help answer significant questions about where, why, and when many animals move, and how they do so efficiently in both space and time. By understanding how animals use the olfactory landscape to make crucial decisions affecting their fitness, we can then manipulate the landscape to modify ecological interactions and, ultimately, ecosystem consequences of these interactions.

Keywords: animal movement; information; landscape ecology; odor; olfaction.

Figure 1.

A snapshot of an olfactory landscape. At any one time, an animal is faced with overlapping odor contours emitted from sources of risk (predators, parasitic infected and/or territorial conspecifics) and reward (mating opportunities, food). These olfactory contours are dynamic in space and time, reflecting predator movements, changes in foraging resource quality and location, and territory shifts. For an animal navigating its surroundings, these dynamic contours of odor can be exploited, providing information on the spatiotemporal distribution of potential threats and opportunities. Consequently, across a landscape, these layers of odor provide a key mechanism for many animals to optimize decision making and movement patterns from afar.

Figure 2.

The four ‘F’ landscapes and the olfactory landscape. Current frameworks of animal behaviour and movement ecology focus on two major questions, ‘why move?’ and ‘when and where to move?’. ‘Why move’ is informed by an animal's internal state (e.g., hunger and fear) (Nathan et al. 2008). ‘When and where to move’ is driven by the need to optimize fitness and avoid being eaten across fluctuating external physical landscapes of Food (foraging resources and water), Fornication (mating opportunities), Fighting (competitors and conspecifics), and Fear (predation risk and parasites). But, a missing link in these frameworks between ‘why move’ and ‘when/where to move’ is discussion around ‘how?’. How does an animal know an area is safe to visit? How does an animal decide if an area has food worth moving to? Specifically, the sensory machinery animals use to sense and respond to information, and the information itself comprised of dynamic layers of volatile compounds indicative of resource and risk across these four ‘F’ landscapes is often left out of the equation. Odor is a major source of information answering the ‘how's’ of behaviour and movement for many animals. Across a landscape, dynamic olfactory contours are a consequence of emissions from everything. These dynamic olfactory contours can provide a real-time source of information, reflecting the spatiotemporal distribution of resource and risk across these four ‘F’ landscapes, informing many animals decisions to move.