Where To Buy Fox Urine In Toronto
Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra.
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Primary productivity usually varies more within a tundra site than among sites. This high local variation in primary productivity suggests that soil condition is one of main determinants of primary production in Arctic tundra ecosystems22. Primary productivity during short growing seasons in tundra ecosystems is often strongly limited by inorganic N availability in the soil, and followed closely by P, as shown by plant tissue analyses23 and fertilization experiments24,25. Measuring concentrations of the inorganic forms of N and P is necessary for a better understanding of the pool of nutrients available to plants in Arctic tundra where, because of cold temperatures and extremely high or low moisture levels, the decomposition rate of organic material is severely restricted26. Although Arctic soils are often rich in organic material and some Arctic plants can make use of the organic form of N, Arctic soils are still fairly poor medium for plant growth due to the fact that organic N in Arctic soil is mostly in insoluble form, and only a small proportion of the soluble organic N occurs in a form that is useable by Arctic plants27.
We predicted that, due to nutrient addition by Arctic foxes, inorganic N and extractable P levels at den sites would be higher than control sites, and as a result vegetation biomass would be higher at den sites. Additionally, we predicted that due to receiving nutrients from marine and allochtonous resources in Arctic fox diet (such as geese and seals), δ15N values would be elevated in plants growing on fox dens, whereas plants on control sites would have lower δ15N signatures, indicative of locally fixed N sources28,29. We also predicted that dens with pups in the previous year would have higher inorganic N and extractable P levels than dens that did not have pups.
Our estimates of the difference in annual plant productivity between den and control areas are conservative. Unlike L. mollis and willow species, D. integrifolia is an evergreen species32, thus not all the above-ground D. integrifolia biomass collected is produced in one growing season. Furthermore, L. mollis dominates on the den sites but it is almost non-existent on control sites, whereas D. integrifolia dominates on the control areas and is not commonly found in high proportions on den sites (Fafard unpubl. data). Therefore, the effect of Arctic fox nutrient deposition on plant biomass is most likely even greater than our estimates.
By constantly depositing nutrients, Arctic foxes maintain the higher inorganic N and extractable P concentrations on den sites compared to control sites. This effect could be carried on for multiple years, considering that dens with and without pups did not differ in inorganic N and extractable P concentrations. Furthermore, the enhancing effect of foxes on nutrient levels does not seem to be restricted to the growing season, since we found fox urine on about 80% of these dens in April (Roth, unpubl. data), suggesting that dens are visited regularly throughout the year.
Nitrogen to phosphorus (N:P) ratios in plant tissues are regularly used as reliable indicators of nutrient limitation for both vascular plants35 and bryophytes36. N:P ratios greater than 16 suggest P limitation, whereas N:P ratios less than 14 indicate N limitation and N:P ratios between 14 and 16 indicate N and P co-limitation35,37. However, due to homeostatic regulation by plants, N:P ratios in plants are not equal to N:P ratios in soil. Homeostatic regulation coefficients (the inverse slope of the log-log relationship between soil and plant N:P) can vary from 1.7 to 4.638, and based on our measured soil N:P ratios, control sites are likely P limited in June, and N limited in August. Den sites, however, are likely to be N limited in both seasons.
In laboratory settings, behavioral changes in response to the presence of predators or predator cues have been primarily assessed in prey animals using tests of exploratory behavior. For example, male mice exposed to a rat, a cat or cat feces increase their avoidance of the area near the odor and limit their exploration of open elevated areas and risk assessment in the elevated-plus maze (EPM; Calvo-Torrent et al., 1999; Belzung et al., 2001; Adamec et al., 2004). Rodents exposed to 2,5-dihydro-2,4,5-trimethylthiazoline (a constituent of fox urine/feces), dog feces, a cat collar, or anal gland secretions from dogs and coyotes show a longer latency to emerge from a shelter, decreased motor activity and visits to the center of an open field, and increased freezing and vigilance behavior (Dielenberg et al., 2001; Fendt et al., 2005). Acute or repeated exposure of male rats to a cat, cat odor, or a ferret reduces their exploratory behavior (Plata-Salamán et al., 2000; Armario et al., 2008). Therefore, the impact of the presence of predators or predator cues leads to measurable changes in exploration detected both in laboratory and in natural environments.
Activity was first recorded over a 3-min pretest habituation period (without the rat puppet) during which risk assessment and escaping behaviors were measured. This period was followed by a predator avoidance test, where the rat puppet was introduced at one end of the runway and accelerated towards the mouse at a 50 cm/s speed until the subject ran away or was brought into contact with it. This test was repeated five times. The distance to the predator at flight initiation was measured.
PO offspring of both sexes exhibited increased Oxt transcript abundance within the PVN, the primary brain region of Oxt expression (Gimpl and Fahrenholz, 2001). These results contrast with impairments in social memory and decreased social interaction reported in adult rat offspring from dams exposed to repeated physical restraint during gestation, that show a reduction in the number of Oxt-positive cells in the PVN (de Souza et al., 2013). However, other evidence has indicated that increased Oxt mediates increased social affiliation following acute immobilization stress (Muroy et al., 2016). PO offspring had unaltered Oxtr transcript abundance within the amygdala. This was unexpected given previous evidence of the role of Oxtr in amygdala in promoting social behavior (Gimpl and Fahrenholz, 2001). The lack of difference in amygdala Oxtr expression, suggests that the increased social investigation observed in this study may occur through another as yet undefined mechanism. For example, increased Oxtr binding in the central amygdala was detected in male rats prenatally exposed to unpredictable stressors (Lee et al., 2007) where binding density is correlated with social investigation (Dumais et al., 2013). This result suggests that binding is influenced by factors beyond the level of hormone and ligand. For example, Oxt binds with low affinity to Avp receptors, which could further mediate the impacts of higher central Oxt expression (Russell and Brunton, 2009). Future studies should however investigate Oxtr transcript abundance in the olfactory bulb and cortex and amygdala sub-nuclei as these differences might be obscured in an analysis of transcript abundance in the entire amygdala. For example, the medial amygdala is necessary for olfactory-based social recognition in both males and females while preserving the olfactory non-social olfactory memory (Ferguson et al., 2001; Choleris et al., 2007). Furthermore, the central amygdala has been associated with the modulation of defensive behavior in the presence of an aversive odor following fear conditioning (Rickenbacher et al., 2017). Finally, the HPA response to predator odor is likely facilitated through main olfactory system-medial amygdala-PVN or olfactory cortex-PVN circuitry (Takahashi, 2014; Kondoh et al., 2016), which would be important to elucidate in the context of PO exposure effects in future studies. Nevertheless, along with the increased PVN Crf transcript abundance, our findings suggest that Oxt participates in the observed increase social investigation and normal social memory detected in PO offspring.
Within the PVN, PO offspring exhibited increased Nr3c2 transcript abundance, with no difference in Nr3c1 transcript abundance. Nr3c1 and Nr3c2 expression and function are known to be dissociated, as they respond specifically to low and high level of glucocorticoids, respectively (Brinks et al., 2007; Mesquita et al., 2009; Berardelli et al., 2013; Juruena et al., 2015). There is some evidence that Nr3c2 is necessary for glucocorticoid regulation of the HPA axis activity during mild stressors, where fewer receptors are associated with a more pronounced corticosterone release. This effect is not observed in response to a stronger stressor (Juruena et al., 2015). This could explain how a change in Nr3c2 transcript abundance may be sufficient to elicit stress-induced behavioral changes in PO offspring. Within the PVN, Nr3c2 expression mediates the sensitivity of the stress response through proactive endocrine feedback (Juruena et al., 2015). For example, higher expression of Nr3c2 promotes resilience, vigilance and selection of the appropriate coping strategy in animals (Juruena et al., 2015; Joëls and de Kloet, 2017). This observation is also in accordance with the behavioral phenotype of increased stress-related behavior and predator odor avoidance previously reported by our group in mouse and rat PO offspring (St-Cyr and McGowan, 2015; St-Cyr et al., 2017). As such, the increased Nr3c2 transcript abundance in the PVN may contribute to the adaptive stress responsiveness observed in PO offspring. 041b061a72