Daily rhythms of metabolic rates: Role of chemical signals in coexistence of spiny mice of the genusAcomys

The common spiny mouseAcomys cahirinus and the golden spiny mouseA. russatus coexist in the extreme arid and hot parts of the Arava Rift Valley in Israel. The coexistence of these two species is through exclusion ofA. russatus from nocturnal activity byA. cahirinus, which is nocturnal. An attempt was made to study the daily activity rhythm response ofA. russatus to chemical signals released byA. cahirinus, in order to understand the mechanism of segregation. For this purpose oxygen consumption, O₂, was studied in individuals ofA. russatus kept alone in a metabolic chamber in a constant ambient temperature of 32°C under two photoperiod regimes: 12L:12D, and constant darkness (D:D). After three days of O₂ recording under these conditions, chemical signals released fromA. cahirinus were passed through the metabolic chamber. This treatment caused a shift in the activity rhythm only ofA. russatus kept at 12:12D, while a decrease in O₂ rates ofA. russatus was noted in both groups. These results suggest that chemical signals released byA. cahirinus may play a role in shiftingA. russatus toward its diurnal activity.     

Use of predator odors to protect chick-peas from predation by laboratory and wild mice

Synthetic stoat odor (3-propyl-1,2-dithiolane and 2-propylthietane) and fox fecal odor (2,5-dihydro-2,4,5-trimethylthiazoline) at various concentrations were applied to chick-peas (Cicer arietinum) at sowing in an investigation aimed at reducing damage caused by house mice (Mus musculus). Stoat odor at 10% concentration exerted a measure of protection, as did 1% fox odor against predation by laboratory mice. Wild mice were less affected by synthetic predator odor and appeared to have a shorter memory for it. Laboratory mice cannot be regarded as surrogate wild mice, when used in experimental situations such as those employed here.     

Laboratory Evaluation of Predator Odors for Eliciting an Avoidance Response in Roof Rats (Rattus rattus)

We evaluated eight synthetic predator odors and mongoose (Herpestes auropunctatus) feces for eliciting avoidance responses and/or reduced feeding by wild captured Hawaiian roof rats (Rattus rattus). In a bioassay arena, we recorded: (1) time until each rat entered the arena, (2) time elapsed until first eating bout, (3) time spent in each half of the arena, (4) number of eating bouts, and (5) consumption. Rats displayed a response to the predator odors in terms of increased elapsed time before initial arena entry and initial eating bout, a lower number of eating bouts, and less food consumption than in the respective control groups. The odor that produced the greatest differences in response relative to the control group was 3,3-dimethyl-1,2-dithiolane [from red fox (Vulpes vulpes) feces and mustelid anal scent gland]. Mongoose fecal odor produced different responses in four of the five variables measured while (E,Z)-2,4,5-trimethyl-³-thiazoIine (red fox feces) and 4-mercapto-4-methylpentan-2-one (red fox urine and feces) odors were different from the control group in three of the five variables measured. These laboratory responses suggest that wild Hawaiian roof rats avoid predator odors.     

Effect of Congeneric Chemical Signals of Different Ages on Foraging Response and Food Choice in the Field by Golden Spiny Mice (Acomys russatus)

The common spiny mice Acomys dimidiatus and golden spiny mice Acomys russatus coexist in the extreme warm and dry parts of the Rift Valley in Israel. However, they are temporally segregated in that the former is nocturnal, whereas the latter is diurnal. Daily rhythms of physiological and behavioral variables in A. russatus responded to semiochemical signals released by A. dimidiatus (in the urine and feces). Both species feed upon the same food items but at different times of the 24-hr cycle. The main aim of the present study was to test under field conditions the foraging response of A. russatus to odors of different ages released by A. dimidiatus. Various feeding and behavioral variables were compared in three groups of A. russatus. The results show that fresh semiochemical signals released by A. dimidiatus decrease the feeding efficiency and increase the rate of smelling from a distance in A. russatus. These results support the idea that temporal segregation between the two coexisting species is at least partly through semiochemicals present in the urine and feces.     

Use of predator odors as repellents to reduce feeding damage by herbivores

This study investigated the influence of the major anal-gland compounds from the stoat (Mustela erminea) and fecal and urine compounds from the red fox (Vulpes vulpes) in generating an avoidance response by montane voles (Microtus montanus), as well as suppressing feeding by montane and meadow (M. pennsylvanicus) voles on apple trees in orchards. In trap bioassays, a 11 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane significantly reduced vole captures. Other mixtures of stoat compounds reduced the number of new voles captured but not total individuals. 2,5-Dihydro-2,4,5-trimethylthiazoline, a component of fox feces, significantly reduced vole captures in one of two bioassays. Deer mice (Peromyscus maniculatus) did not show a negative response to any predator odor. In overwinter field bioassays, mixtures of 2-propylthietane and 3-propyl-1,2-dithiolane clearly reduced vole feeding on apple trees in four test blocks. 2,5-Dihydro-2,4,5-trimethylthiazoline and a synthetic fox urine mixture also significantly reduced vole attack in respective orchard blocks. Similarly, the intensity of vole feeding, in terms of amount of bark and vascular tissues removed from trees, was reduced by 60% to 97% in predator odor treatments compared with the control. Our study reports the first long-term (four to five months) use of synthetic semiochemicals as area repellents for crop protection from vole feeding damage.     

Orientation of the fiddler crab,Uca cumulanta: responses to chemical and visual cues

Behavioral responses of the fiddler crab Uca cumulanta to flat geometric shapes mimicking natural objects were measured in a circular arena by using zonal recovery as a behavioral measurement. Crabs were tested either in presence or absence of odors from two common predator species, the blue crab Callinectes sapidus, and the pufferfish Sphoeroides testudineus. The study tested the hypothesis that U. cumulanta have different behavioral responses to visual cues in the presence of chemical cues associated with predators. Escape direction tests demonstrated that U. cumulanta is able to show zonal recovery behavior based upon astronomical references. When tested in water lacking predator odor, crabs failed to exhibit a consistent orientation if a single silhouette target was interposed in the landward direction. However, when animals were tested in different predator odor concentrations, an orientation response was obtained at 10 and 20 g/liter/hr blue crab odor and 10 g/liter/hr pufferfish odor, demonstrating U. cumulanta ability to detect the potential presence of its natural predators by this odor. Thus, the hypothesis was supported, and the results suggest that behavioral responses to chemical and visual cues are involved in predator avoidance.     

Responses of Cambarid Crayfish to Predator Odor

The responses of individuals of four sympatric species of cambarid crayfish to the introduction of the odor of a common predator, the snapping turtle Chelydra serpentina, were recorded in the laboratory. Adult Orconectes virilis spent significantly more time in a lowered posture and reduced the frequency of nonlocomotory movements following introduction of snapping turtle odor but showed no change in behavior upon introduction of the odor of painted turtle (Chrysemys picta). Recently released young O. virilis did not respond to snapping turtle odor initially but did so after turtle odor and conspecific alarm odor had been paired. Individuals of O. propinquus did not respond to snapping turtle odor. Initial tests with O. rusticus did not yield any response to snapping turtle odor but after experience with paired turtle and alarm odor, individuals showed a decrease in nonlocomotory movements when just snapping turtle odor was introduced. Individuals of Cambarus robustus spent less time in the lowered posture, less time in their burrow, and more frequently executed nonlocomotory movements, in response to snapping turtle odor. The differences in responses to the odor of a common predator are correlated with ecological differences among the crayfish species.     

Effects of predator fecal odors on feed selection by sheep and cattle

The effectiveness of predator fecal odors in modifying feeding selection by sheep and cattle was investigated in two trials. In trial 1, animals could select from feed bins contaminated with coyote, fox, cougar, or bear fecal odor, and oil of wintergreen, or select the control feed. All odors were rejected (P<0.01) by sheep and cattle, except bear odors by sheep. In trial 2, animals could select feed during 10-min periods in an open 11-m × 16-m arena. Fecal odor did not influence approaches to feed bins, or head entries into bins. Only coyote fecal odor reduced (P<0.05) the time spent feeding in the contaminated bin, and increased (P<0.05) consumption from the control bin by both cattle and sheep. Some animals on some test days refused to feed from either feed bin, although cattle and sheep closely inspected bins. Results suggest that fecal odors may not prevent livestock from entering a treated area but may reduce the time spent grazing in such an area.This research was supported in part by the Utah Agric. Exper. Sta., Utah State University, Logan, Utah 84322. Approved as journal article no. 3721     

Chemical and Olfactory Characterization of Odorous Compounds and Their Precursors in the Parotoid Gland Secretion of the Green Tree Frog, Litoria caerulea

When stressed or challenged by a predator, the Australian green tree frog, Litoria caerulea, emits a characteristic nutty odor from its parotoid glands. This study identifies the source of the odor as the cyclic amide 2-pyrrolidone (2-PyrO). In addition, we demonstrate the presence of 2-PyrO's straight chain form, -aminobutyric acid or GABA, in the frog's glandular secretion and propose an odorant–precursor relationship. What role both compounds play in the frog's defensive strategy remains unknown. Prolonged exposure to the odor is shown to result in adverse effects that may be attributed to a GABAergic mechanism. It is our hypothesis, however, that the odor acts as an aposematic signal, indicating the toxicity of the frog's nonvolatile secretion.     

Alarm substance of the marine mud snail,Nassarius obsoletus: Biological characterization and possible evolution

The gastropod snailNassarius obsoletus shows a dramatic self-burial response to the presence of crushed conspecifics. After it was shown that this burial alarm response could be reliably replicated in laboratory tests, a further characterization of the alarm substance was undertaken. Dilution experiments showed a very high response threshold resulting in a short effective radius of the substance in agreement with earlier field reports. Longevity experiments showed that the substance had lost some activity after 16 hr standing over marsh mud in sea water at room temperature; it became inactive after 24 hr. Superthreshold concentration in sea water was not necessary to keep the snails buried: Mud apparently provides an adsorption surface which can remain a stimulus source for previously unalarmed snails, and snails tend to remain buried after a short exposure to alarm substance, even when given a fresh environment. The substance is present in the snail's blood and tissues and is passively released. A potential natural predator capable of such release isCarcinus maenas, the green crab. Predator odor alone did not cause burial alarm responses. Preliminary chemical analysis indicates that the substance is water soluble, heat stable, and of high apparent molecular weight (over 100,000). A comparison with fish alarm substance and response is made in a discussion of the possible evolution of chemically triggered alarm responses. It is argued thatN. obsoletus may have developed an alarm response to an existing nonspecific substance rather than a true alarm pheromone.This paper is based in part upon a thesis submitted by D.S. to Boston University for the degree of Master of Arts.     

Acquired Predator Recognition by Fathead Minnows: Influence of Habitat Characteristics on Survival

In this study we conditioned fathead minnows (Pimephales promelas) to recognize the odor of a perch (Perca flavescens) by exposing them to perch odor coupled with minnow alarm cue. We then staged encounters between the predator and prey in order to assess whether the predator odor training had any effect on survival of the prey. We tested for a survival effect in the presence and absence of shelter. Our results indicate that fish trained with alarm signals to recognize predators gained a survival benefit during staged encounters with a predator and that habitat characteristics influenced the survival of conditioned fish.     

An evaluation of repellents to suppress browsing by possums

The efficacy in feeding suppression trials with possums (Trichosorus vulpecula Kerr) of six synthetic odorous chemicals uniquely associated with various of the Mustelidae species and of the red fox (Vulpes vulpes) has been evaluated with respect to several proprietary repellents. The predator odors, two proprietary repellents, and two other repellent formulations (olive oil in petroleum jelly and a synthetic fermented egg odor cocktail) were applied as 5% w/v solutions in paraffin to the foliage ofPinus radiata seedlings and the extent of browse compared with that on seedlings treated with Treepel, an effective egg-based repellent already available commercially. All four of the mustelid predator odors [()-2-n-propylthietane, ()-3-n-propyl-1,2-dithiolane, 2,2-dimethylthietane, and 3,3-dimethyl-1,2-dithiolane] and the volatile compound from fox urine (³-isopentenyl methyl sulfide) were shown to be more or at least equally effective compared to Treepel. This was true also of one commercial repellent Gori, which contained bitrex and the synthetic fermented egg formulation. The most effective compounds will be evaluated when administered with adhesives and surfactants in the further development of possum repellents with longer field lives.     

Use of odor baits in traps to test reactions to intra- and interspecific chemical cues in house mice living in outdoor enclosures

House mice (Mus musculus) living in outdoor enclosures were tested for urinary chemical cue preferences using odor-baited traps. In the first experiment, with only volatile cues available, odors from conspecific males and females of various age classes and reproductive conditions were tested; no preferences were exhibited. In the second experiment mice had both nonvolatile and volatile cues available from the same sources as in experiment I. All age and sex class and female reproductive condition groups exhibited odor cue preferences except juvenile females. There were no specific odor cue preferences exhibited by any of the responder types with regard to odors from juvenile females. In the third and fifth experiments, mice were presented with nonvolatile plus volatile or only volatile urine odor cues, respectively, from four genera,Mus, Peromyscus, Microtus, andHomo. Mice of all age classes and both sexes preferredMus musculus odor, were neutral towardMicrotus ochrogaster odor, and avoided odors fromPeromyscus leucopus andHomo sapiens; these patterns were the same regardless of whether only volatile or both volatile and nonvolatile cues were presented. The fourth and sixth experiments involved testing volatile cues only and volatile cues plus nonvolatile cues from human sweat or feces from dogs, cats, or shrews. Mice avoided the human sweat and feces from cats and shrews, but were neutral toward the odor of dog feces. There were effects on whether mice were trapped in the interior of the enclosure or on the perimeter for some odors tested in these six experiments. The findings provide insights regarding possible functions of odor cues in the behavioral ecology of house mice. Odor-baiting traps can be an effective tool with respect to testing some, but not all questions pertaining to olfactory cues and house mouse social biology.     

Cattle and Amblyomma variegatum Odors Used in Host Habitat and Host Finding by the Tick Parasitoid, Ixodiphagus hookeri

The response of mated naive Ixodiphagus hookeri females to cattle and Amblyomma variegatum nymphal odors was tested in a Y-tube olfactometer. I. hookeri females were attracted to cattle urine, dung, and odors from tick-free feeding sites of A. variegatum nymphs on cattle, e.g., dewlaps, front heels, and hind heels. Tick-free scrotal odors did not attract the parasitoids. Furthermore, odors from off-host unfed and fed A. variegatum nymphs did not attract the parasitoids, despite an increase in the number of the nymphs to amplify any odor signal. A blend of odors from feeding on-host nymphs and cattle scrota attracted the parasitoids. In T-tube bioassays, I. hookeri females were attracted to hexane washes and fecal extracts of A. variegatum nymphs.     

Responses of beaver (Castor canadensis Kuhl) to predator chemicals

Free-ranging beaver (Castor canadensis) in two different beaver populations in New York State were exposed to predator chemicals to test feeding inhibition. Solvent extracts of feces were applied to stem sections of aspen, the preferred food tree of beavers, permitting smelling and tasting the samples. Predator odors were from wolf (Canis lupus), coyote (Canis latrans), dog (Canis familiaris), black bear (Ursus americanus), river otter (Lutra canadensis), lynx (Lynx canadensis), and African lion (Panthera leo). The experiment was repeated. The predator odors reduced feeding compared to untreated or solvent-treated controls. One population consumed 17.0% of the samples with predator odor and 27.0% of the controls in summer, and 48.4% and 60.0%, respectively, in autumn. The other population accepted 3.15% of the predator odor samples and 11.05% of the controls in summer. Coyote, lynx, and river otter odors had the strongest effects. Diesel oil and bitter-tasting neem extract had weaker effects. Predator odors are promising as feeding repellents for beaver.     

Selective odor perception in the soil collembolaOnychiurus armatus

The olfactorial response of the fungivorous soil collembolanOnychiurus armatus was examined in a bioassay covering volatile compounds identified in the odor blends of two of its preferred fungal speciesMonierella isabellina andVerticillium bulbillosum. The odor of the fungi was trapped using activated carbon filters, extracted with diethyl ether, and subjected to GC-MS analysis. About 50% of the compounds resolved by GC were identified by a combination of electron impact and chemical ionization mass spectrometry. In a Y-shaped olfactometer the collembolans were attracted to a variety of common odors, such as CO₂ and 2-methyl-1-propanol, and a species-specific odor, such as 1-heptene, and arrested by, for example, decanal and 2-octene. The response was not improved by pairwise combinations of common and specific odors. An amount of 0.5 ng of ethyl acetate or 3 pg of 1-pentanol was sufficient to attract the collembolans. The specific compounds ofV. bulbillosum, 1-heptene and 1-octen-3-ol, may be key stimuli explaining whyO. armatus prefersV. bulbillosum.     

Influence Of Diet-Related Chemical Cues from Predators on the Hatching of Egg-Carrying Spiders

Previous studies have shown that animals may make adaptive adjustments in response to chemical cues from predators, but hatching responses to diet-related chemical cues from predators have not been previously demonstrated. In the system studied here, the predator is an araneophagic jumping spider (Salticidae), Portia labiata, and the prey organism is a subsocial spitting spider, Scytodes pallida (Scytodidae). The spitting spider carries its eggs in its chelicerae, and carrying eggs is known to make it more vulnerable to predators. It is also known from an earlier study that the prior diet of the predator alters how dangerous the individual predator is to the spitting spider. In the experiments reported here, incubation time was shorter when volatile cues from the predator were present and longer in control tests when no chemical cues from the predator were present. The previous predators diet also influenced incubation time: when in the presence of volatile cues from individuals of P. labiata that had previously fed on individuals of S. pallida, incubation time was shorter than when in the presence of volatile cues from individuals of P. labiatathat had been feeding instead on house flies.     

Behavioral and electrophysiological responses of Aphids to host and nonhost plant volatiles

Alate and apterous virginoparae ofAphis fabae Scop, and alate virginoparae ofBrevicoryne brassicae (L.), walking in a linear track olfactometer, were attracted by odor from leaves of their host plants.A. fabae responded to odor from undamaged but not damaged bean leaves. Gynoparae (autumn migrants) ofA. fabae, however, did not respond to their host plant (spindle,Euonymus europaeus) odor. Odors of certain nonhost plants masked the attractiveness of the host plant leaves, but tansy (Tanacetum vulgare) and summer savory (Satureja hortensis) volatiles repelledB. brassicae andA. fabae, respectively. 3-Butenyl isothiocyanate attractedB. brassicae andLipaphis erysimi (Kalt.), the latter species being more sensitive in both behavioral and electrophysiological studies. Isothiocyanate receptors were found on the antennae ofA. fabae, which was repelled by these compounds, 4-pentenyl isothiocyanate being the most active.     

Electroantennogram responses of the cabbage seed weevil,Ceutorhynchus assimilis,to oilseed rape,Brassica napus ssp.Oleifera,volatiles

Electroantennograms (EAGs) were recorded from male and female cabbage seed weevils (Ceutorhynchus assimilis Payk.) in response to volatiles isolated and identified from the odor of oilseed rape (Brassica napus ssp.oleifera DC. cv. Ariana). Relatively large EAGs were obtained on stimulation with volatiles produced by the oilseed rape crop at the time when seed weevils were actively searching for host plants. Artificial rape odor without certain key volatile compounds was in most cases significantly less stimulatory than odor containing these volatiles. There were significant differences in the EAG response of the sexes ofC. assimilis to the green leaf volatiles of oilseed rape and several terpenes present in rape flower odor. The importance of the qualitative and quantitative composition of host-plant odor in host location byC. assimilis is discussed.     

Olfactory Responses of Plutella xylostella Natural Enemies to Host Pheromone, Larval Frass, and Green Leaf Cabbage Volatiles

The parasitoids Trichogramma chilonis (Hymenoptera: Trichogrammatidae) and Cotesia plutellae (Hymenoptera: Braconidae), and the predator Chrysoperla carnea (Neuroptera: Chrysopidae), are potential biological control agents for the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae). We present studies on the interactions between these bioagents and various host-associated volatiles using a Y olfactometer. T. chilonis was attracted to a synthetic pheromone blend (Z11–16:Ald, Z11–16:Ac, and Z11–16:OH in a 1:1:0.01 ratio), to Z11–16:Ac alone, and to a 1:1 blend of Z11–16:Ac and Z11–16:Ald. C. plutellae responded to the blend and to Z11–16:Ac and Z11–16:Ald. Male and female C. carnea responded to the blend and to a 1:1 blend of the major components of the pheromone, although no response was elicited by single compounds. Among the four host larval frass volatiles tested (dipropyl disulfide, dimethyl disulfide, allyl isothiocyanate, and dimethyl trisulfide), only allyl isothiocyanate elicited significant responses in the parasitoids and predator, but C. plutellae and both sexes of C. carnea did respond to all four volatiles. Among the green leaf volatiles of cabbage (Brassica oleracea subsp. capitata), only Z3–6:Ac elicited significant responses from T. chilonis, C. plutellae, and C. carnea, but C. plutellae also responded to E2–6:Ald and Z3–6:OH. When these volatiles were blended with the pheromone, the responses were similar to those elicited by the pheromone alone, except for C. carnea males, which had an increased response. The effect of temperature on the response of the biological agents to a mixture of the pheromone blend and Z3–6:Ac was also studied. T. chilonis was attracted at temperatures of 25–35°C, while C. plutellae and C. carnea responded optimally at 30–35°C and 20–25°C, respectively. These results indicate that the sex pheromone and larval frass volatiles from the diamondback moth, as well as volatile compounds from cabbage, may be used by these natural enemies to locate their diamondback moth host.