Ecological Scent Detection: Sniffing out the Elusive Pima Pineapple Cactus

The usefulness of detection dogs to our society seems just to grow and grow. Detection dogs have been trained to find explosives, illegal drugs, currency, gourmet fungus, human remains, contraband electronics, firearms, termites, bed bugs, cancerous tumors and low blood sugar emergencies in people with diabetes. And the dogs do this even if the scent has been covered up or scrubbed away.

Dog researchers use some pretty amazing analogies to convey a dog’s sense of smell. It can be anywhere from 10,000 to 100,000 times our own. Put another way; dogs can detect some odors in parts per trillion. Or, if you can detect a teaspoon of sugar in your coffee, a dog could detect a teaspoon of sugar in a million gallons of water.

Photo: Lauralea Oliver

The most recent application of the dog’s super power is ecological scent detection. Ecological scent detection is the use of dogs to help in the location and subsequent research of wildlife. For instance, scat is abundant in the wild and contains valuable data. Wildlife scat detection by dogs represents a non-invasive method of study for many species where previously live capture or other invasive methods predominated. Dogs achieve more accurate, comprehensive results, supplementing traditional survey methods. They can be particularly useful in conditions where the effectiveness of a human search effort relying on visual detection is diminished. Also, dogs can work in complex environments with elusive species and discover evidence that ecologists alone may be unlikely to find. Detection dogs have been used successfully to locate northern spotted owls, and salamanders, and even killer whales, among many other wildlife and plant species. In the case of killer whales, the dogs (riding in boats) can detect the scent of their scat which floats on the surface for about 30 minutes!

Ecological scent detection is at the heart of a new collaboration between the U.S. Fish and Wildlife Service, the Arizona-Sonora Desert Museum and California-based ecological consulting firm, H. T. Harvey & Associates ( ). H. T. Harvey & Associates has a team of in-house detection dogs, affectionately referred to as their Harvey Dogs. Each Harvey Dog is rigorously trained to detect the target species and is paired with an ecologist also specially trained in detection dog work. The target, in our case, is the Pima pineapple cactus (Coryphantha scheeri var. robustispina).

Photo: ASDM/Kat Rumbley

Pima pineapple cactus is a federally registered endangered species that the Museum grows for U.S Fish and Wildlife for just such purposes. Found as a single or multi-stemmed plant, this low-growing hemispherical cactus measure 4-18 inches tall and 3-7 inches in diameter. It occurs only in Pima and Santa Cruz counties, and some parts of Mexico, on alluvial plains and hillsides in semi-desert grasslands, desert scrub and the transition area between the two.

The distribution of the cactus is patchy, with highly variable densities, and widely distributed across the areas of suitable habitat. Few locations have significant populations, and those tend to be clumped within a smaller area. Due to topography, hydrology, plant community type, and elevation, there are extensive areas within the overall range of the cactus that do not qualify as habitat. Young plants are rarely found, and it is uncertain if this is due to difficulty in locating small plants or if the seedling establishment is low.

This cactus is vulnerable to ground disturbing activities that remove or degrade natural vegetation cover, including mining, poor livestock management, and urban/exurban development that fragments remaining habitat areas. Expansion of non-native invasive plants, such as Soft Feather Pappaus Grass (Enneapogon cenchroides) and Buffelgrass (Pennisetum ciliare) that alter the fire frequency and intensity, predation by insects and small mammals, and extended drought are also threats to the cactus.

In the past, surveys of the cactus were done by humans transecting an area of appropriate habitat, with each transect being from a different direction. It has taken humans as many as six transects to locate all individual cactus in a given area. But dogs have been used with great success in finding several species of plants. And while human-only visual surveys for rare plants are often biased toward adult and flowering life stages, dogs have been able to detect odor originating from a target plant’s roots as well as dead and desiccated plants.

Dog training takes place over an approximately 16-week period. During this time the dogs are tested for target scent recognition and must alert their handlers to the location of the target with 100% accuracy over the course of 10 consecutive tests. Having passed this period of training the teams of humans and dogs move on to two or more weeks of training in a field setting where plants are camouflaged with items they would encounter when searching in real Pima pineapple cactus habitat. The third phase of training is scent discrimination between Pima pineapple cactus and other cactus species they will encounter in the real habitat.

Using scent detection dogs is likely to improve the efficiency of the surveys while reducing costs. Training is fully funded and will start in December 2016 and go through March 2017. We will know the success of the endeavor by the end of March 2017.

If results are positive, dogs may soon be Pima pineapple cactus’ dearest friends.

Written by: Mark Fleming, Curator of Botany

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