1/27/2020

1

Environmental Factors’ Effects on Eastern Gray Squirrel Infant Populations and Health ConditionsJenny McFarland

Otterbein University '20

Zoo & Conservation Science, Biology

Stormy Gibson

Ohio Wildlife Center

Assistant Executive Director

Photo credit: Ohio Wildlife Center Hospital

Why Squirrels?• 5 species in US1

Gray, Fox, Red, Ground and Flying You most likely have more than one of these in your area!

• In 2018 and 2019, squirrels were the OWC's 2nd most admitted mammal (630 and 792 infants/juveniles/adults)2

1 (Steele & Koprowski, 2001).

2 Ohio Wildlife Center 2018 Annual Report, Facebook announcement 1/21/2020

1

2

1/27/2020

2

Introduction: Ecosystems• Temperature and precipitation are key for seasonal reproduction and

caching. They also help keep disease, predation and competition in check

• Larger, healthier and more experienced individuals usually out-compete younger, weaker, sicker and less experienced individuals for resources

• Predation impacts the reproductive and survival rates of prey and predators

1 (Lima, Morgan-Ernest, Brown, Belgrando & Stenseth, 2008; Bionda & Brambilla, 2012; Wallace et al., 2016; Schmidt et al., 2018)

2 (Steele & Smallwood, 2004; Parker & Nilon, 2008; Dantzer, Boutin, Humphries & McAdam, 2012; Lamontagne et al., 2013; Freeman & Bachman, 2016)

3 (O’Dongohue, Boutin, Krebs & Hofer, 1997; Kamler, Ballard & Wallace, 2007; Schmidt et al., 2018; Jokinen, Hanski, Numminen, Valkama & Selonen, 2019)

Introduction: Mast• Mast: vegetative food resources1

• Soft mast: fleshy fruits, such as berries and legumes2

• Hard mast: nuts and encased fruits, such as acorns and walnuts2

• Mast is important for food caching, survival and reproductive resources, and population success3

1 (Selonen, Wistbacka & Korpimaki, 2016)

2 (Mast Tree Network, 2009)

3 (Edelman & Koprowski, 2006; Xiao, Gao, Jiang & Zhang, 2009; Selonen& Wistbacka, 2015)

Photo credits to Jenny McFarland

3

4

1/27/2020

3

Species of Interest: Eastern Gray Squirrels (Sciurus carolinensis)• Have 2 birthing seasons: mid-March thru

mid-May, and late-July thru mid-September1

• Experience a 50-75% mortality rate under 1 year of age2

• Adult females do not reproduce more than once per year3

• 44 -day gestation3

• Reproductive age reached at 9-11 months3

1 (Brown and Yeager 1945; Moore 1957; Pokines, Santana, Heller & Price, 2016)

2 (Mosby, 1969; Barkalow, Hamilton & Soots, 1970; Thompson, 1978; Sharpe & Sherrill, 2017)

3 (Webley & Johnson, 1982; Steele & Koprowski, 2001)

Photo credit: Ohio Wildlife Center Hospital

HypothesesEnvironmental factors impact Eastern gray squirrel (EGS) infant populations.

Since environmental factors influence mast production, competition and predation, these three ecosystem factors will also influence EGS infant populations.

Photo credit: Ohio Wildlife Center Hospital

5

6

1/27/2020

4

Predictions1) higher amounts of produced mast will lead to more EGS offspring

2) increased temperatures, rainfall and daylight will lead to more EGS offspring

3) lower windspeeds will lead to healthier EGS offspring

4) large predator populations will correlate with large EGS offspring populations

5) large competitor populations will correlate with large EGS offspring populations

Photo credits to Jenny McFarland

Methods• All animal data collected from Ohio Wildlife Center (OWC)

7

8

1/27/2020

5

Methods• All weather data collected from the

National Weather Service database

• All acorn mast data collected from the Ohio Department of Natural Resources (ODNR)

• Data was entered into Excel sheets, where comparative data was run through t-tests of unequal variances to generate a p-value and tested for standard deviation, or they were put into scatter plots and given an R² value

Tables 1 & 2: The annual number of EGS infants admitted and the average monthly EGS infants admitted

Year Number of EGS infants

2013 385

2014 361

2015 301

2016 391

2017 469

2018 281

Month Avg % of Annual EGS infants

January 0.0

February 0.987

March 7.147

April 16.038

May 5.122

June 1.7

July 8.792

August 40.043

September 18.362

October 1.902

November 0.503

December 0.052

9

10

1/27/2020

6

Table 3: The percent of EGS infants admitted July-December (fall births)

* Significant (p≤0.05)

Year % of EGS infants admitted J-D

2013 73.25*

2014 65.37*

2015 62.13*

2016 79.54*

2017 68.66*

2018 60.58*

Figure 1: Average percentage of EGS infants that died/were euthanized or were released. Only significantly more infants were released if admitted as Clinically Healthy (X).

11

12

1/27/2020

7

Figure 2: Percent of seasonal EGS infant admissions of Clinically Healthy and summed Unhealthy individuals. Error bars represent standard deviation (±16.084). Significant differences were found (p=0.0107, X).

Figure 3: Number of monthly EGS infant admissions that were deemed Clinically Healthy or summed under Unhealthy. Error bars represent standard deviation per month. Significance was found between the Clinically Healthy and Unhealthy admissions of July (p=0.0339) and October (0.0411) (September being 0.04938).

0

50

100

150

200

250

300

January February March April May June July August September October November December

Nu

mbe

r of

EG

S I

nfa

nt

Adm

issi

ons

Healthy Unhealthy

XX

X

13

14

1/27/2020

8

Figure 4: Comparison of EGS infants admitted annually, EGS juveniles and EGS adults. Error bars represent standard deviation. Significance was found annually to the number of juveniles (p=0.0000237, X) and adults (p=0.0000564, Y).

Table 4: Average monthly EGS infant admissions versus average monthly environmental and weather factors

R² Value Type of Correlation

Temperature (ºF) +0.3109 Moderate

Rainfall (inches)* +0.4254 Moderate

Windspeed (mph) -0.3159 Moderate

Daylight (hours)* +0.2929 Low

Mast (% of red & white oaks producing acorns)**

-0.5206 Moderate

* Weather data displayed is for the month prior to the EGS intake. For example, how April’s rainfall correlates to the May EGS infant intake.** Mast data is for annual percent of oaks producing acorns rather than monthly

15

16

1/27/2020

9

Table 5: Average monthly EGS infant admission numbers versus average monthly admission for other species

R² Value Type of Correlation

Red squirrels +0.2119 Low

Red-tailed hawks +0.4625 Moderate

Owls (barred, barn, great-horned, eastern screech and snowy)

+0.3135 Moderate

Red fox +0.0049 None

Discussion: Mast• Red oak acorns can be stored longer in

caching, while white oak acorns are more optimal for immediate eating

• Soft mast is usually used by June/July

• Acorn and other hard mast production peaks in August-October

• EGS infants born after July in search of food will find hard mast, which they may not be developed enough to eat yet

Photo credits to Jenny McFarland

17

18

1/27/2020

10

Discussion: Infant Survival• Late spring frosts can cause low soft mast

production levels

• July-December infants may not have enough time to build up their fat reserves and their cache reserves

• Spending more time looking for food resources could cause them to encounter competitors, predators, and other hazards more often

• Colder temperature fronts, heavy rainfall, and other extreme weather cases may displace infants

Photo credit: Ohio Wildlife Center Hospital

Conclusions

• Moderate support was found that temperature, rainfall, windspeed and mast production are correlative to the number of EGS infants and when they are born.

• Moderate support was also found that the number of aerial predators is correlative to the number of EGS infants admitted.

Photo credit: Jenny McFarland

19

20

1/27/2020

11

Further Directions• Soft mast vs hard mast

• Other forms of hard mast, such as pinecones and walnuts

• Hunting influences, such as hunting season or approximately how many EGS are taken annually

• Whether EGS females still breed once per year or twice

• Human development and deforestation progression

Photo credit: Ohio Wildlife Center Hospital

Acknowledgements• Dr. Beaux Berkeley, Otterbein University

• Dr. Andrew Calinger-Yoak, Otterbein University

• Ms. Sherry Buckley, Ohio Wildlife Center

• Drs. Lou and Cindy Rose, Otterbein University

Funding provided by Otterbein University’s Biology and Earth Science summer research grant, the OWRA travel and conference grants, the Debbie Chandler Memorial Scholarship and the Miller-Winter Leader grant

21

22

1/27/2020

12

Thank you for your time! Any questions?

Photo credit: Ohio Wildlife Center Hospital

23