Owners of gardens and orchards often try to deter herbivores, especially deer, by placing droppings of carnivores next to the crop to be protected with pheromones. The success again is a matter of subjective judgment. Pheromone laboratory experiments showed that naive black-tailed deer fed signiﬁcantly less than usually, or not at all, near droppings of predators. The most effective droppings were those of cougar (Felis concolor) and coyote, both of which occur in the range of black-tailed deer (Muller-Schwarze 1972).
New pheromone opportunities may arise with the isolation and identiﬁcation of the alarm pheromones of deer, which are known to inhibit feeding (Miiller-Schwarze 1971). Recently, biologically quite remote extracts of rotten salmon carcasses have been demonstrated (by the U.S. Fish and Wildlife Service in cooperation with the Weyerhaeuser Company) to repel deer. Protection from black-tailed deer browsing was reported to be ‘greater than that of other contact repellents available’ (Rochelle 1973). So far no true pheromones but only scents or decomposition products of other species have been used in ﬁeld tests. These odors may be effective by mimicking alarm pheromones or predator odors. One problem with using predator odors is that droppings and scent marks are examined by herbivores at close range (a few centimeters). Such repellents from feeding on treated plants but would not keep them out of an entire area (no ‘fence function’).
Pheromone Odors Practice
In farm practice, odors have been used to facilitate maternal behavior. An ewe can be made to accept a strange lamb if the lamb is covered with the hide or the birth ﬂuid of her own lamb. On the level of the species, Alpaca (Lama pacos) and Vicuﬁa (Lama vicugna) can be crossbred by killing a newborn alpaca and using its hide to cover newborn male vicuﬁa. A lactating alpaca female will then accept the vicuﬁa, which in this way becomes sexually imprinted on alpacas and will later mate with alpaca females to produce desired hybrids. The cross, called ‘paco-vicuﬁa’ has wool of almost the quality of the vicuﬁa, and in the quantity typical of the alpaca (Hodge 1946).
Farmers and breeders know that sniffing and licking play an important role in the reproductive behavior of domesticated animals. However, the domestic pig is the only species for which pheromone research has yielded applicable results. Pat- terson (1968) identiﬁed an odoriferous compound (30:-hydroxy-5oz-androst-16-ene) which occurred only in the submaxillary gland of the boar. Signoret (1970a) describ- ed a higher frequency of head-to-head approaches than of sniffing the genitalia (70 vs. 30%) in encounters between boars and oestrous gilts. An aerosol containing the steroid identiﬁed by Patterson was subsequently developed and tried in breeding programs. Check out human pheromones.
The pheromone aerosol was blown into the face of sows that had not assumed the typical, rigid ‘mating stance’, which is a prerequisite for mating. Forty-six per cent of formerly unresponsive females assumed the mating stance after treatment, while none of the individuals treated with a blank aerosol did so (Melrose et al. 1971). In the same study, a spray with preputial fluid and urine had a similar effect. Signoret (1970b) reported similar results: 48.3—52.5% of the sows responded with the mating stance to warm preputial secretion, but only 22.5% to the cold secretion. When placed in a pen where a boar had been, the figure increased to 62.2%. Perry et al. (1972) showed that removal of the submaxillary glands from males early in life results in a later inability to release the mating stance in sows, and induces aggressivity by the females toward the male.