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Lesson Plans

Winter Forage for Gray Squirrels

Introduction:

Many of our local birds and mammals remain active throughout the winter. They must find enough food to provide for their required level of activity, in addition to maintaining a warm body temperature in a cold environment. How do they find enough food? What do they eat? In this activity, you will attempt to answer these questions with respect to one particularly common species – the Gray Squirrel, Sciurus carolinensis.

You are probably familiar with the Gray Squirrel’s habit of hiding acorns and other nuts for the winter. What you may not know is that these animals require about two pounds of food each week. If you consider the length of our winter, and the lack of new foods (nuts, fruits, seeds, flowers, buds, mushrooms) being produced at this time of year, the squirrels must store a significant mass of nuts to survive the season. A forest’s collective “crop” of nuts and seeds fed on by wildlife is referred to as mast.

Objectives:

To quantitatively sample the mast production of a local forest.
To estimate the carrying capacity of the forest for Gray Squirrels
To indentify the oak species to which different acorns belong

Materials:

field guide to trees
measuring tape
1 m² hoop
plastic bags
spring scale / balance
marking pen
journals

Procedure:

Establish a 50 meter transect line through the forest
At 5 meter intervals, drop your 1 m²to the ground.
Thoroughly pick through the leaf litter in each designated square meter area, and collect all acorns, beech nuts, hickory nuts, and other nuts and seeds present.
Identify the species represented by the mast.
Measure the mass for each area (collect in labelled bags for measurement in the bag, or measure in the field using a spring scale - remember to subtract the mass of the bag so as to measure only the mass of the acorns, nuts, and seeds)
Record your data
Perform the necessary calculations to estimate the mast production of the local forest, and its carrying capacity for Gray Squirrels.

Data:

Table 1:

Sample #	Species Present as mast	Dominant Species	Total Mass, g/m²
1
2
3
4
5
6
7
8
9
10
			Average mass = _____g/m²

Class average: (Add average mass for all gourps, divide by number of groups) = _________g/m²Mast produced per hectare (10,000 m², 2.54 acres) : Class averatge g/m² X 10,000 = _____ g/ha. Divide by 1000 to get _______ kg/ha

Carrying capacity for squirrels:

a: Assume a weeklu requirement of 4.4 kg (2 lbs) for each squirrel
b: Divide the class average data by 4.4 kg

__________kd/ha / 4.4 = ______________ squirrels per hectare

c: Now, divide yur result by the estimated number of weeks left in winter, or until you think the squirrels will have significant new sources of food.

__________ squirrels/ha (from step "b") / _________ weeks = __________ squirrrels/ha/week (estimated squirrel carrying capacity)

Analysis:

1. What is the dominant food source for squirrels in our forest?

2. What species compete most directly with the squirrels for the mast crop?

3. Do you think our estimate for the forest's carrying capacity is too high, too low, or fairly accurate?

4. Explain your answer to question #3. What variables might be affecting our data? What assumptions did we make that might not be accurate?

5. Describe how you would redesign the field examination to obtain more reliable results.

6. Record your observations and experiences in your journal.