To Monitor the Distribution and Abundance of Brevard S Resident White Squirrel Population

WHITE SQUIRRELS

PURPOSE

·  To monitor the distribution and abundance of Brevard’s resident white squirrel population

INTRODUCTION

Origins

The city of Brevard, NC hosts an established colony of white squirrels, a color morph that currently makes up more than 20% of the native Eastern gray squirrel (Sciurus carolinensis) population. The white squirrels are not albinos as are other well-studied white colonies (Stencel and Ghent 1987). Brevard’s variant has pigmented eyes, a distinctive head patch, and dorsal stripe.

According to local folklore, all of today’s white squirrels are descended from a single pair trapped from northern Florida and eventually released in Brevard in 1951 (The White Squirrel Shoppe). The existence of white squirrels with the same distinctive pattern scattered throughout central and northern Florida supports the Florida connection (White Squirrel Research Institute). However, this widespread distribution casts doubt on the rest of the legend. The supposed circus caravan wreck and an exotic oriental origin may simply be embellishments to make the story more interesting.

Since that time, the Brevard white morph has not only increased in abundance within the city, but it also has dispersed over a wide area. Today, white squirrels with similar markings are found from Cashiers in the west to Hendersonville in the east, a span of approximately 50 miles (White Squirrel Research Institute). However, the disjunct nature of their distribution suggests that their dispersal may have been assisted by trap and release by admiring humans.

Figure 1. Gray and white color morphs of the Eastern gray squirrel (Sciurus carolinensis)

Genetics of Coat Color

There is much variation in both the white and gray morph, and little is known of their underlying developmental genetics. However, these variants do appear to segregate as separate Mendelian units. Mixed litters occur in which individuals are either white or gray, not intermediate. It is often assumed that, like albinos, the white morph is recessive, but breeding experiments are sparse, uncontrolled, and inconclusive. In fact, an analysis of the rapid increase to the current stable dimorphism suggest that the white morph may actually be dominant (Glesener 2001a).

Biology of Gray Squirrels (Halloran 2001)

Gray squirrels, common throughout the eastern United States, are considered to be arboreal, or tree, squirrels. They are highly adapted for climbing trees, with tough curved claws and flexible joints giving them the ability to have headfirst descent. Powerful hindlimbs are used for leaping. Their bushy tails are primarily for balance, but they are also used to communicate and can be held over the body like a blanket for warmth.

These squirrels have two breeding seasons, winter and summer. However, an individual female will rarely have two successive litters unless food is plentiful. A typical litter consists of 2 or 3 pups. The gestation period is 42 days. The young remain in the nest for an additional 8 weeks before following the mother on brief foraging forays in the immediate vicinity. By 10 weeks they are usually weaned. Summer litters often overwinter with the mother before dispersing. Both sexes mature just inside one year. The average life span is 4 years, although individuals of this species can live up to 7 or 8 years (15 years in captivity). Gray squirrels have a dominance hierarchy: females in estrus will mate first with the dominant male, but they will pursue further matings with subordinate males. Although these squirrels have a social dominance hierarchy, they are not territorial. Their home ranges overlap.

Gray squirrels are active year round and are generalist omnivores. They feed heavily on nuts, seeds, flowers, and buds of many tree species. They can also feed on bones, bird eggs, nestlings, and frogs. Of course, in urban areas like Brevard, backyard feeders are also an important source of nutrition, particularly in poor mast years. Soft foods are usually consumed on the spot. Nuts may cached, i.e., buried in shallow underground holes, for latter use. They are probably relocated by smell with many going undetected thereby serving as a means of seed dispersal for nut-bearing trees.

Eastern gray squirrels have three types of nests: winter dreys, summer dreys, and dens. Dreys are twig and leaf nests built in tree forks at least 25 feet off the ground. They look like large, loosely constructed bird nests. Winter dreys are more complex and better insulated than summer ones. However, tree dens (cavities in the trunk of a tree), when available, are preferred in the winter months.

Figure 2. Picture of a squirrel drey built in a tree fork.

Figure 3. Picture of two squirrels with a tree den.

Brevard Annual Squirrel Count

In 1997, four Brevard College students and one faculty conducted the 1st Annual Brevard Squirrel Count as part of a directed study. It was patterned after a long-term study of the albino colony in Olney, IL (Stencel and Ghent 1987). A study area of approximately 3.0 square miles centered on downtown Brevard was divided into 35 sectors. Each fall, teams of volunteers methodically walk through these same Sectors on three consecutive Saturday mornings, recording all squirrels observed, white and gray. The Count is not an actual census. It represents the percentage of white versus gray morphs seen on the mornings of the Count, but it is an obvious underestimate of the absolute numbers. However, we have every reason to believe that the percent white of those observed approximates the actual percent white, and the more complete the Count, the more accurate that estimate will be. From year to year, the abundance of squirrels has varied widely in concert with available hard mast (Greenberg 1999, Glesener 2001b). However, the percent of the white morph has remained remarkably constant in the 20-25% range.

Study Purpose

You will be participating in this year’s Annual Squirrel Count being conducted by Brevard College’s White Squirrel Research Institute. This survey will help us monitor the distribution and abundance of Brevard’s resident white squirrel population. The data from this year’s count will be available to the public on our website at http://tornado.brevard.edu/whitesquirrel/ within a few months. In the meantime you may wish to examine the website for results of previous counts and other squirrel information. We do not expect to see every squirrel that resides in the study area, but the more complete the count, the more accurate the data.

FIELD PROCEDURE

1. Please arrive shortly prior to 8:00 am to receive your assignment.

·  Each count will be conducted in an 8:00-10:00 a.m. time range. Please bring a watch.

·  Unless told otherwise, report to the first floor of the Moore Science Building.

·  Enter the North door (Library end) and queue up at the table in the foyer area (by the rock collection).

·  You will be assigned to a particular Sector and will receive a Map for that specific Sector.

·  If there are enough participants, you may be assigned a partner.

·  An identification tag and clipboard help you look more "official."

·  Attach the your map and the data sheet to a clipboard with the map page on top.

·  If you are transporting yourself, consult a city map for directions to your Sector.

·  Leave the building by the South door.

2. During the two hour interval of the count, you are to walk the entire area of the Sector Map one time.

·  Take a moment and plan your path ahead of time.

·  Avoid doubling back which could result in some squirrels being counted twice.

·  Not visiting some areas means that some active squirrels will be missed.

·  Do not be afraid to visit backyards and wooded areas, but please do not climb fences or enter other restricted areas. Ask permission when appropriate (you will be surprised in how cooperative most folks are). Be polite.

·  Comply with resident’s requests.

3. After a sighting, record the location of the squirrel on the Map with a W for white or a G for gray as soon as possible.

·  If you can distinguish adults and juveniles use upper case (W or G) for adults and lower case (w or g) for juveniles. Because it is difficult to distinguish "W" from "w", so circle the w if it is a juvenile.

·  If you are uncertain as to whether it is an adult or juvenile, just mark "G" or "W". While this additional information may be useful for future studies, we are not actually distinguishing between adults and juveniles in this count.

·  Then write another W or G in the appropriate box down below on that same map page indicating the time interval of the observation.

·  IT IS JUST AS IMPORTANT TO OBSERVE AND RECORD GRAY SQUIRRELS AS WHITE ONES.

·  If you have time, record the location of nests on your map with an N.

4. Observational Tips.

·  Remember that tree squirrels nest in trees but forage mostly on the ground. Look carefully on the ground near and in large trees, espeically hardwoods, and around feeders, etc.

·  Look carefully in areas where you observe nests

·  Clucking sounds may be coming from a squirrel (however, you must see the squirrel to determine if it is white or gray).

5. If you see a squirrel on an adjacent Sector, record its approximate location off the edges of your Map BUT DO NOT INCLUDE IT IN THE TALLY BOXES FOR YOUR SECTOR.

·  If your Sector and an adjacent one are separated by a street, then the midline of the road marks the boundary.

6.  Record “Road kills” on the Map and tally boxes with WK or GK.

·  There is also a separate “Totals” box for road kills in the “Observations” table on the datasheet.

7. If you note any interesting behaviors, predators (including cats, dogs, etc.) that may effect squirrel activity in that area, etc, mark an O (for “Observation”) on the Map

·  Include a complete description on the Data Sheet

·  Don’t let these extra observations interfere with the main objective, i.e., completing the count.

8. When you finish your assignment, return to the command center, and tabulate your observations.

·  Use the numbers from the 8 interval boxes on the map sheet to fill out the top three tables of the data sheet.

·  The most important numbers are those of the "Totals" column of the third table representing the total number of white and total number of gray seen during your count.

·  If you did not distinguish between adult and juveniles, enter all data in the adult boxes.

·  Make sure you record the Sector number and fill out the rest of the requested information including any comments, suggestions, etc., before turning it in.

·  Your name (and that of all partners) must appear at the bottom of the data sheet to get credit.

·  If you are doing a make-up count or are doing your count at a non-standard time or day, be sure to complete the weather information at the top of the data sheet. If you are doing a standard Saturday morning count, this will be the same for everyone.

·  Staple the map and data sheet together with the datasheet on top and turn in immediately.

In case of heavy rain or high winds, we may postpone the count until the following day. If there is a question and you are coming in from some distance, try calling 883-8292 Extension 2301 sometime around 7:15 a.m. A message regarding the status of the count should be available. If you encounter any problems that need immediate assistance during the count or get lost, please try 883-8292 Extension 2278 or 2377.

Strip Line Transect Census

As mentioned above, the Count reliably estimates the percent of the white versus gray morphs but underestimates the actual abundance. All squirrels will not be out during the two hours of the Count and all squirrels out will not be observed. There are many other ways to estimate population density. One of the simplest from a methodological point of view is the strip line transect census. Some of you may not be able to participate in the regular count or may be seeking extra credit and will be assigned a ~1 kilometer line transect to census. You will be given maps similar to those referred to above with a transect line charted for you to walk. Theoretically, the line should be straight but that is not usually possible. The important thing is that "observable distances" from any sections of the line not double back allowing the same squirrel to be observed twice. On the assumption that you see all squirrels located directly on the transect line and that the probability of detection falls off as some function of the distance of the squirrel from that line, there are statistical procedures that use the number and distances of squirrels observed to predict the actual number.

·  Select a time to conduct the census in consultation with your instructor. Early mornings or late afternoons on a fair weather day are best.