Influence of adjacent crop type on occurrence of California ground squirrels on levees in the Sacramento Valley, California

2013 ◽  
Vol 38 (1) ◽  
pp. 111-115 ◽  
Author(s):  
Michael C. McGrann ◽  
Dirk H. Van Vuren ◽  
Miguel A. Ordeñana
Keyword(s):  
Ground Squirrels ◽  
Sacramento Valley ◽  
Crop Type ◽  
California Ground Squirrels

The Information Afforded By a Variable Signal: Constraints On Snake-Elicited Tail Flagging By California Ground Squirrels

Behaviour ◽  
1981 ◽  
Vol 78 (3-4) ◽  
pp. 188-224 ◽  
Author(s):  
David F. Hennessy ◽  
Matthew P. Rowe ◽  
Richard G. Coss ◽  
Daniel W. Leger ◽  
Donald H. Owings
Keyword(s):  
Functional Significance ◽  
Ground Squirrels ◽  
Current Status ◽  
Structural Parameter ◽  
Behavioral Correlates ◽  
Temporal Parameters ◽  
The Status ◽  
Tail Movement ◽  
Number Of Cycles ◽  
California Ground Squirrels

AbstractIn this paper we report the results of our first efforts to evaluate the functional significance to signaler and perceiver of variation in tail flagging (Fig. 1 and Fig. 2A-C) by California ground squirrels (Spermophilus beecheyi). We first report a series of anecdotes in which we describe the circumstances of a variety of tail movements by California ground squirrels, including the different kinds of tail flagging. Secondly and primarily we identify the information afforded by snake-elicited tail flagging. Tail flagging is a signal used by California ground squirrels primarily when they are harassing a potential snake predator (Fig. 4). It attracts other squirrels who may also begin harassing the snake. The risk to squirrels in encounters with snakes continuously varies, and the squirrels adjust their behavior accordingly. Consequently in this situation we expected to find shifts in the information afforded by different tail-flagging variants. We view the information afforded by tail movement and other signals as a consequence, not of selection for making that information available, but of the correlations resulting from situational constraints on the signaler's behavior, e.g., correlations between tail movement variation and variation in significant events. We used two complementary approaches to help determine the information afforded by tail flagging. In one, we asked whether information important to percipients is afforded by tail flagging. In the second, we searched for situational correlates of tail-flagging variants. We applied the second approach to each individual separately and to the group comprising these individuals. This allowed us to look for idiosyncrasies in signaler behavior. Although a relatively simple signal, tail flagging varies along several structural and temporal parameters. From video recordings we quantified a structural parameter- number of movement cycles in a bout of tail flagging - and two temporal parameters- rate and temporal clustering of tail flagging. Our results show that squirrels adjust their tail-flagging behavior in the following ways. 1. When a rattlesnake rattles, harassing squirrels increase the number of cycles per bout of tail flagging. 2. Lone snake-directed squirrels temporally clump their flagging bouts more than snake-directed squirrels accompanied by other snake-directed individuals. 3. The structure of flagging varied with the squirrel's behavior vis-a-vis the snake. While dealing directly with a snake, squirrels emitted relatively few 1-cycle bouts of flagging. While in the vicinity and monitoring snake-related events, but engaged primarily in other activities such as feeding or grooming, squirrels emitted relatively greater numbers of 1-cycle bouts. As one would predict from this difference, individuals were farther from the snake on the average while emitting 1-cycle bouts than while emitting 2-cycle bouts. Adults used far more 2-cycle bouts than 1, and 3 or higher. In the field, bouts of 4-cycles or greater were very rare. We found that the information afforded by a bout of tail flagging was much greater when we considered structural variation, than when we did not. For example, flaggers were more likely on the average to "pause" before than after tail flagging. However, although the same difference held for 1-cycle bouts, just the reverse was true for 3-cycle bouts, and there was little difference in the probability of pausing for 2-cycle bouts. We found similar differences for other behavioral correlates of tail flagging. A percipient could much more precisely predict a tail flagger's behavior by considering signal variation. Our results indicate a percipient can infer from a high proportion of 3-cycle bouts that the flagger is beginning an episode of snake-directed activity, whereas 1-cycle bouts indicate a temporary cessation of snake-directed behavior. We expect to find even greater situational specificity of tail flagging when we simultaneously consider multiple structural dimensions, such as axis of movement and number of cycles. When we looked at the information afforded by a bout of tail flagging separately for individual squirrels, it was clear that the specific behavioral profiles associated with different variants of tail flagging were somewhat idiosyncratic. Thus, a percipient squirrel should be able to infer more from the tail flags of a familiar squirrel than an unfamiliar squirrel. We propose that signals are used to elicit a particular kind of performance from the target(s). The effectiveness of such action depends upon a knowledge of the current status of the individual's target(s). We conclude that variation in tail flagging is constrained in at least three ways: 1) by the number and quality of targets of tail flagging (e.g., snakes, squirrels); 2) by the signaler's certainty about the status of the target(s) (by eliciting behavior in targets, tail flagging may be used in part to extract information about the target's state); and 3) by the quality and availability of feedback (the success of tail flagging is continually assessed on the basis of feedback). The understanding of the functional significance of tail flag variability therefore becomes the problem of understanding how the flagger uses signal adjustments to deal with changes in its circumstances in terms of these three general constraints.

Disease Surveillance of California Ground Squirrels (Spermophilus beecheyi) in a Drive-through Zoo in Oregon, USA

2017 ◽  
Vol 53 (3) ◽  
pp. 667-670
Author(s):  
Julia Ter Beest ◽  
Andrew Cushing ◽  
Modesto McClean ◽  
Wendy Hsu ◽  
Robert Bildfell
Keyword(s):  
Disease Surveillance ◽  
Ground Squirrels ◽  
Spermophilus Beecheyi ◽  
California Ground Squirrels

scholarly journals Quantitative Shedding of Two Genotypes of Cryptosporidium parvum in California Ground Squirrels (Spermophilus beecheyi)

2001 ◽  
Vol 67 (6) ◽  
pp. 2840-2843 ◽  
Author(s):  
Edward R. Atwill ◽  
Sergio Maldonado Camargo ◽  
Ralph Phillips ◽  
Laura Herrera Alonso ◽  
Kenneth W. Tate ◽  
...  
Keyword(s):  
Cryptosporidium Parvum ◽  
Ground Squirrels ◽  
Spermophilus Beecheyi ◽  
California Ground Squirrels

ABSTRACT Sixteen percent of California ground squirrels (Spermophilus beecheyi) were found to be shedding an average of 53,875Cryptosporidium parvum oocysts/g of feces. Male squirrels had a higher prevalence and higher intensity of shedding than did female squirrels. The majority of C. parvum isolates matched a bovine-murine genotype, with a few isolates resembling a porcine genotype. Higher intensities of shedding by males may enhance dissemination and genotypic mixing of this protozoa given males' proclivity to disperse to nonnatal colonies.

Development of Antisnake Defenses in California Ground Squirrels (Spermophilus Beecheyi): II. Microevolutionary Effects of Relaxed Selection From Rattlesnakes

Behaviour ◽  
1993 ◽  
Vol 124 (1-2) ◽  
pp. 137-162 ◽  
Author(s):  
Richard G. Coss ◽  
Naomie S. Poran ◽  
Kevin L. Gusé ◽  
David G. Smith
Keyword(s):  
Population Level ◽  
Ground Squirrels ◽  
Species Discrimination ◽  
Spermophilus Beecheyi ◽  
Relaxed Selection ◽  
Virtual Absence ◽  
Rare Site ◽  
California Ground Squirrels ◽  
Two Populations

AbstractNonvenomous Pacific gopher snakes (Pituophis melanoleucus catenifer) and venomous northern Pacific rattlesnakes (Crotalus viridis oreganus) have coexisted in a predator-prey relationship with California ground squirrels (Spermophilus beecheyi) for many thousands of generations. This long-term relationship has fostered in ground squirrels the evolution of antisnake defenses that consist of physiological resistance to rattlesnake venom and behavioral tactics of probing and harassing that might facilitate snake-species discrimination. Snake harassment by adults might also protect pups by interfering with snake hunting activities. Some ground squirrel populations have colonized habitats where rattlesnakes, but not gopher snakes, are rare or absent. Initial research indicates that squirrels experiencing relaxed selection from rattlesnakes are very aggressive toward their remaining nonvenomous snake predator, the gopher snake. Two experiments investigated the effects of relaxed selection from rattlesnakes by examining: 1) changes in level of venom resistance, 2) the reorganization of antisnake behaviors in lab-born pups and wild-caught adults from different sites, and 3) the role of natural experiences on the development of antisnake behavior in a rattlesnake-adapted population. Level of venom resistance was examined by an in vitro radioimmunoassay of serum-to-venom binding of two populations of Douglas ground squirrels (S. b. douglasii). The ancestors of one population are estimated to have experienced relaxed selection from rattlesnakes for about 9,000 years based on genetic distance and radiocarbon analyses. The antisnake behavior of 60-73 day-old lab-born pups from these two populations was video taped during presentations of a caged rattlesnake or gophcr snake for alternate 5-min trials in a seminatural laboratory setting. Two groups of wild-caught adult Beechey groundsquirrels (S. b. beecheyi) were studied using the same protocol for examining antisnake behavior. One group was obtained from a population that recently colonized a rattlesnake-rare site and exhibits moderate venom resistance. The second group came from a population that exhibits very low venom resistance and inhabits a rattlesnake-free site; relaxed selection from rattlesnakes for this population is estimated to span approximately 60,000 years. Comparisons of Douglas ground squirrels from rattlesnake-abundant and rettlesnakerare sites revealed that venom resistance declined approximately 59% after an estimated 9,000 years of relaxed selection from rattlesnakes. Lab-born Douglas pups from the same rattlesnake-rare site were more aggressive toward the gopher snake than toward the rattlesnake whereas pups from the population experiencing predation from both species of snake treated both snakes as similarly dangerous. Unlike pups, wild-caught adults from the rattesnake-adapted population harassed the rattlesnake more intensely than the gopher snake, a phenomenon that may reflect their experience with snakes in nature and larger body size that reduces their vulnerability to envenomation. Wild-caught Beechey ground squirrels that recently colonized a rattlesnake-rare site did not differentiate the rattlesnake and gopher snake whereas Beechey ground squirrels whose ancestors have experienced prolonged relaxed selection from rattlesnakes were more aggressive toward the gopher snake. Consistent with previous findings, prolonged relaxed selection from rattlesnakes, but not gopher snakes, appears to have reduced the inhibition to harass large gopher snakes. This microevolutionary shift in increased aggressiveness toward the gopher snake could result from the virtual absence of any risk in misidentifying rattlesnakes from gopher snakes.

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