Diurnal Squirrels Research Articles

Impact of a Single Episode of Different Intensity of White Light Pulse at Night on Masking Response in the Diurnal Mammal, Funambulus pennantii

Objective: Light affects mammalian circadian rhythms through entrainment and masking. Photic masking increases locomotor activity in diurnal species (positive masking) while reducing activity in nocturnal species (negative masking). Fewer studies have investigated masking in diurnal rodents. We investigated the masking response in a diurnal rodent, <i>Funambulus pennantii</i> when subjected to white light pulses of different intensities at night between zeitgeber time (ZT) 12 and ZT 15.Methods: Adult male squirrels, <i>F. pennantii</i> (n=10/group, three groups) were placed in individual cages with running wheels under standard 12:12 h light-dark (LD) conditions. Recording of the locomotor activity rhythm was carried out using a ClockLab setup. Following a week of stable entrainment to the LD cycle, the animals of each group were given a sham exposure. After 10 days, animals of group I, II, and III were exposed to 3-h white light pulses of 100 lux, 10 lux, and 1 lux, respectively, between ZT 12 and ZT 15. Following the exposure, the animals were allowed to run undisturbed for 7 days.Results: Compared to the shamexposed group, exposure to 3-h 1 lux, 10 lux, and 100 lux artificial light pulses at night caused positive masking, stimulating wheel running in an intensity-dependent manner. Additionally, nighttime light pulses of 100 lux and 10 lux reduced onset accuracy, reduced the amplitude of the rhythm, and also altered the phase angle relationship to light.Conclusion: The positive masking caused by light exposure at night in diurnal squirrels is intensity-dependent up to at least 100 lux and is associated with a dampening of circadian rhythms.

Fine-Scale Interactions between Leopard Cats and Their Potential Prey with Contrasting Diel Activities in a Livestock-Dominated Nature Reserve.

Habitat use and the temporal activities of wildlife can be largely modified by livestock encroachment. Therefore, identifying the potential impacts of livestock on the predator-prey interactions could provide essential information for wildlife conservation and management. From May to October 2017, we used camera trapping technology to investigate fine-scale spatiotemporal interactions in a predator-prey system with the leopard cat (Prionailurus bengalensis) as a common mesopredator, and its prey with contrasting activity patterns (i.e., nocturnal rats and diurnal squirrels) in a livestock-dominated nature reserve in Northern China. We found that the prey species showed different habitat preferences with the leopard cats. The nocturnal rats had strong positive effects on the site-use of the leopard cats, while the influence of livestock on the diurnal squirrels' site-use changed from strong positive effects to weak effects as the livestock disturbance increased. The temporal overlap between the leopard cats and the nocturnal rats was almost four times that of the leopard cats and the diurnal squirrels, regardless of the livestock disturbance. Our study demonstrated that the fine-scale spatiotemporal use patterns of the leopard cats were consistent and highly correlated with the nocturnal rats under livestock disturbance. We suggest that appropriate restrictions on livestock disturbance should be implemented by reserve managers to reduce the threat to wildlife and achieve multi-species coexistence.

Chronic altered light–dark cycle differentially affects hippocampal CA1 and DG neuronal arborization in diurnal and nocturnal rodents

ABSTRACT The hippocampus, an extension of the temporal part of the cerebral cortex, plays a crucial role in learning and memory. Structural and functional complexity within the hippocampus is greatly affected by a variety of external environmental stimuli including alteration in the light–dark (LD) cycle. The effect of altered LD cycle in learning and memory associated cognitive impairment has been reported in rodents. However, a comparative study of underlying neuronal changes between nocturnal and diurnal species is not well explored. The objective of the present study was to explore the morphological changes in hippocampal CA1 and DG neurons in response to prolonged constant condition viz. constant light (LL) and constant darkness (DD) in diurnal squirrels and nocturnal mice. Animals (n = 5/group) were placed in chronocubicle under 12:12 h LD, LL and DD. After four weeks, brain tissues were collected and processed for Golgi-Cox staining to analyze morphological changes in CA1 and DG neurons. The total and basal dendritic length, basal dendrite number, branch end, the diameter of apical dendrite and spine density were analyzed. The results showed a significant reduction in structural complexity of CA1 and DG neurons of squirrels exposed to prolonged constant darkness, whereas mice showed a significant increase as compared to LD. However, a significantly reduced neuronal complexity was observed in both squirrels and mice exposed to prolonged constant light. The results obtained were further confirmed by Sholl analysis of CA1 and DG neurons. The present study suggests that prolonged constant light may cause adverse effects on the neuronal complexity of both diurnal and nocturnal animals, but constant darkness may cause adverse effects mainly to the diurnal animals.

Differential response of diurnal and nocturnal mammals to prolonged altered light-dark cycle: a possible role of mood associated endocrine, inflammatory and antioxidant system

ABSTRACT The circadian system maintains internal 24 h oscillation of behavior and physiology, and its misalignment with external light-dark (LD) cycle results in negative health outcomes. In order to elucidate the effect of prolonged constant condition and the differences in the response between nocturnal and diurnal species, we studied the effects of constant light (LL) and constant darkness (DD) on a diurnal (squirrel) and a nocturnal (mouse) rodent species, focusing on the endocrine, inflammatory and antioxidant systems associated with depression-like behavior. Squirrels and mice (n = 10/group) were placed in chronocubicle under 12:12 h LD cycle, LL and DD. After 4 weeks, animals were subjected to sucrose preference test and blood and brain tissues were collected for measuring melatonin, corticosterone, proinflammatory cytokine, tumor necrosis factor-α (TNF-α) and the activity of primary antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD). The results show that in diurnal squirrels, prolonged constant darkness reduced sucrose preference, CAT, and SOD, increased corticosterone and TNF-α levels, but caused no significant change in the melatonin compared to LD condition. In contrast, in nocturnal mice constant darkness caused no significant changes in sucrose preference and corticosterone levels, increased melatonin, CAT and SOD levels but decreased TNF-α levels. Chronic LL caused a similar response in both squirrels and mice: it decreased sucrose preference, melatonin, CAT and SOD levels but increased corticosterone and TNF-α levels. Together, the study demonstrates differential effects of altered light-dark cycle in a diurnal and a nocturnal rodent on interrelated endocrine, inflammatory and antioxidant systems associated with depression-like behavior, with constant light having adverse effects on both species but constant darkness having a negative effect mainly in the diurnal squirrels.

Small Mammal Activity in South-Central Idaho during the 2017 Solar Eclipse

We collected quantitative data on small mammal activity during the 2017 solar eclipse at a locality in south-central Idaho, at the center of the path of totality where the eclipse reached totality near midday. The day before the eclipse, temperature and light intensity approached daily maximum values during the 3-h period that would encompass the solar eclipse, and only diurnal squirrels were active during this interval. During the eclipse, changes in temperature and light were similar to those that normally occur before dusk and following dawn. Results suggest that diurnal species may have curtailed their activity during the eclipse, and species with facultative activity responded as they would with the approach of dusk. Despite their numerical dominance, nocturnal species were not detected during the eclipse, perhaps due to the brevity of the event or the stronger influence of endogenous activity cycles.

The oxidative damages caused by ultraviolet radiation type C (UVC) to a tropical rodent Funambulus pennanti: Role of melatonin

Data suggests that UV radiation causes oxidative damage of the cells due to the release of inflammatory cytokines which in turn generates reactive oxygen species (ROS) that damages lipids, proteins and DNA. On the other hand, melatonin a potent antioxidant from the pineal gland under most of the conditions acts as a free radical scavenger. Our data suggests that melatonin pre-treatment (s.c. injections) significantly protected the diurnal squirrels from oxidative damages caused by UVC irradiation of 1528mJcm−2 that induced suppression of delayed type hypersensitivity (DTH) responses. It also protected the rodents from UVC radiation induced increase in thiobarbituric acid reactive substances (TBARS) levels in spleen accompanied with a significant decrease in Superoxide Dismutase (SOD) activity indicating the occurrence of superoxide anion mediated damages following UVC exposure. Melatonin administration reduced the radiation induced oxidative stress in the spleen tissue as analyzed by reduced lipid damages and higher SOD activity. Under in vivo (100μg/100g body wt.) and in vitro (250pg/106 cells) conditions, melatonin pre-treatment prevented spleen tissues and splenocytes from radiation induced cell death.In conclusion we may suggest that melatonin could be one of the potent antioxidant and radio protector that may reduce UV radiation induced toxicity to the cells and hence may be clinically important.

Diversity and density of diurnal squirrels in a primary hill dipterocarp forest, Malaysia

Squirrels (Order Rodentia; Family Sciuridae) are among the group of small mammals that have high species diversity in the Malaysian tropical rain forests (Corbet & Hill 1992). In Peninsular Malaysia alone a total of 14 diurnal and 11 nocturnal species has been recorded (Medway 1983). In Peninsular Malaysia, several studies on squirrels have been done which emphasized vertical stratification (Harrison 1962, Lim et al. 1977, MacKinnon 1978, Saiful et al. 2001a), diversity (Zubaid & Ariffin 1997), home range sizes (Tamura 1993, Saiful et al. 2001b), social behaviour (Tamura & Yong 1993) and impact of human disturbance on habitat (Johns 1987). These studies were conducted in lowland and hill forests that have been logged. There are, however, few studies on squirrel abundance in terms of their density in Peninsular Malaysia especially in primary ill forests. Therefore, the purpose of the present study is to provide baseline data and information on squirrel richness, diversity and abundance in the Malaysian primary hill forest.

Body temperature and behaviour of golden hamsters (Mesocricetus auratus) and ground squirrels (Spermophilus tridecemlineatus) in a thermal gradient

Golden hamsters and thirteen-lined ground squirrels were maintained individually in a thermal gradient (14 degrees C to 33 degrees C) for several weeks under a 14L:10D light-dark cycle. Animals of both species showed robust daily rhythms of body temperature and locomotor activity with acrophases consistent with the habits of the species (diurnal acrophases in the diurnal squirrels and nocturnal acrophases in the nocturnal hamsters). Hamsters showed a robust daily rhythm of temperature selection 180 degrees out of phase with the rhythms of body temperature and locomotor activity. Squirrels did not show a daily rhythm of temperature selection. These results raise the hypothesis that a daily rhythm of temperature selection is exhibited by nocturnal but not by diurnal endotherms.

Field Observations on the Malayan Giant Squirrel, <i>Ratufa bicolor gigantea</i> (M'Clelland) and Some Other Diurnal Squirrels of Jalpaiguri District, West Bengal

Field Observations on the Malayan Giant Squirrel, <i>Ratufa bicolor gigantea</i> (M'Clelland) and Some Other Diurnal Squirrels of Jalpaiguri District, West Bengal

Analysis of Bark Eating in a Tropical Squirrel

Although bark eating is quite common among mammals, few species include it as a major item in their diet. The diet of the small squirrel Sundasciurus lowii on Siberut Island, Indonesia, consists mainly of bark. Physical characteristics, nutrient concentrations, and the presence of defense compounds were investigated in bark from 711, 13, and 57 food and nonfood trees, respectively. The results suggest that the squirrels select bark on large, smooth-barked trees with low levels of hydrolysable tannins, whereas concentrations of fat, crude protein, crude fibre, carbohydrate, and calorific value examined in a set of bark samples had no detectable influence on food tree selection. FEEDING ON BARK IS WIDESPREAD AMONG MAMMALS although none has been reported to consume bark to the exclusion of more nutritious items like fruit, herbs, seeds, or grasses. Bark has been recorded as an item in the diet of orangutans (Rijksen 1978), elephants (Hubback 1941, Olivier 1978), rhinoceros (Hubback 1939, Strien 1974), rabbits (Thompson & Worden 1956), squirrels (MacKinnon 1978, Payne 1979, Farentinos et al. 1981), and many species of deer. In the majority of cases, however, no attempt has been made to analyze the physical or chemical features important in bark selection. A study of the ecological separation of three species of diurnal squirrels on Siberut Island, Indonesia (J. Whitten 1981), found that a major food type in the diet of one small species, Sundasciurus lowii (total length, 23 cm), was bark (an average 49% of stomach contents and over 90% of food trees). It was never observed to eat fruit, and stomach analyses revealed that animal remains occupied an average of only 39 percent of the stomachs' volume. S. lowii does not strip bark from large areas in the same way as do common red and grey squirrels, but removes only small flakes, even from trees whose bark would easily strip. Bark is not carried away from the tree and used in nest building, nor has any evidence been found that this behavior is associated with intraspecific aggression. None of the food trees (either trees on which we saw S. lowii feeding or those whose bark showed clear signs of squirrel feeding) produced sap, and no evidence pointed to squirrels' seeking exudates to feed upon (cf. I Received 7 November 1984, revision received 12 December 1985, accepted 8 January 1986. 2 Present address: School for Resource and Environmental Studies, Dalhousie University, Halifax, Nova Scotia, Canada. Lacher et al. 1984). Thus, all bark removal seems to be associated with feeding. This paper describes an analysis of bark and bark eating by S. lowii. METHODS AND MATERIALS Diurnal squirrels were studied on Siberut Island, 100 km west of West Sumatra, for a total of 12 mo during 1976 and 1977. The study area has been described by J. Whitten (1981) and A. Whitten (1982a, b), and the general methods of squirrel observation have been described by J. Whitten (1981). In order to investigate the selection of bark food trees by S. lowii, the following data were recorded from all trees of at least 5 cm DBH in four 0.25ha plots and from all known food trees: species, girth, tree height, canopy height (distance from lowest major bough to topmost leaves), canopy width, bark roughness on a scale of 1 (smooth) to 7 (very rough), thicknesses of the outer bark (that which could be split away from the inner bark) and of inner bark, and ease with which the outer bark could be split away from the inner bark (easy or difficult). In addition, signs of feeding on bark (Fig. 1) and presence of moss, lichen, and climbers were estimated on a scale of 0 (none present) to 3 (very abundant). Similarly, the ease of access for a squirrel from the surrounding vegetation was judged on a scale of 0 (impossible without coming to the ground) to 3 (possible with great ease). Bark samples were dried initially in an oven over an oil lamp for 2 days, after which the samples were taken to the mainland to be dried in an open gas oven for 2 more days. Although we assumed that all signs of bark feeding were made by S. lowii, other species may have contributed. BIOTROPICA 19(2): 107-115 1987 107 This content downloaded from 157.55.39.247 on Wed, 27 Apr 2016 06:49:50 UTC All use subject to http://about.jstor.org/terms

Ecological separation of three diurnal squirrels in tropical rainforest on Siberut Island, Indonesia

Reduced species diversity on islands is well documented. The present paper examines the ecological separation of diurnal squirrels on Siberut Island, Indonesia, and contrasts the results with those of studies on the neighbouring mainland.

The photoreceptors of diurnal squirrels: Outer segment structure, disc shedding, and protein renewal

The photoreceptor outer segments of five species of diurnal squirrels were studied by light and electron microscopy. In all species rod outer segments could be distinguished from cone outer segments by the extent of disc-membrane continuity and by their pattern of protein renewal as determined by autoradiography. Rods showed the characteristic band of radioactive protein within the outer segments, while the cones showed only a diffuse pattern of outer segment labeling. Rod as well as cone outer segments were found to shed packets of discs intermittently. The shedding process appeared to be qualitatively similar in rods and cones. Multiple invaginations of the outer membrane, probably signifying the assembly of new discs, were detected at the base of rod outer segments. Single partially formed invaginations, analogous to those found in rods, also were found at the base of cone outer segments. Thus, cone as well as rod outer segments may assemble and shed discs in the mature animal.

Retinal projections to subcortical optic nuclei in diurnal and nocturnal squirrels.

Retinal projections to subcortical optic nuclei in diurnal and nocturnal squirrels.

A Study of the Diurnal Squirrels, Sciurinae, of the Indian and Indochinese Subregions.Joseph Curtis Moore , George H. H. Tate

<i>A Study of the Diurnal Squirrels, Sciurinae, of the Indian and Indochinese Subregions.</i>Joseph Curtis Moore , George H. H. Tate

DUPLEX FUNCTION IN THE GREY SQUIRREL'S ELECTRORETINOGRAM.

THE grey squirrel (Sciurus carolinesis leucotis) was initially considered to have an all-cone retina, based on evidence obtained by light microscopy1,2 and electroretinography2. In support of this, a difference spectrum obtained by reflexion densitometry was found to peak at 535 mµ3. Afterwards a difference spectrum of a photopigment extracted from this retina peaked at 504 mµ, however, and resembled rhodopsin4. Thereafter a group of diurnal squirrels including the grey squirrel was found to have double-peaked ERG spectral sensitivity curves, suggesting that there was more than one receptor mechanism in these retinae5. Similar ERG results have been reported for other diurnal squirrels6,7. Recently, conditioning experiments on the grey squirrel demonstrated a peak wave-length sensitivity at 502 mµ (ref. 8), and rod-like in addition to cone receptors were found by electronmicroscopy9. This report shows that there are at least two receptor systems contributing to the grey squirrel's ERG which behave similarly to the rod and cone components of the ERGs of duplex retinae.

Spectral sensitivity curves of diurnal squirrels

Spectral sensitivity curves were constructed for four species of ground squirrel, two species of tree squirrel and one species of chipmunk using the stimulus intensity required to produce a constant etoctroretinogram as the criterion. All these species have an apparently pure-cone retina although the retinal structure of the two tree squirrels differs somewhat from that of the ground squirrels and chipmunk. There was no evidence of a Purkinje shift. The spectral sensitivity curves of all seven species were very similar. The curves showed two maxima, one at about 535 mμ, the other at about 490 mμ. The relative heights of these maxima varied from one experiment to another but the factors responsible for this variation could not be determined. Adaptation to blue light depressed the maximum at 490 mμ while adaptation to green or orange light depressed that at 535 mμ. Evidence was obtained that the mechanisms responsible for the two maxima were to some extent antagonistic. The possible nature of these two mechanisms is discussed in the light of recent work on the photosensitive substances extractable from the retina of the common gray squirrel. There was some evidence for a further mechanism maximally sensitive between 450 and 460 mμ at least in some of the species investigated.