Tree Squirrels and Habitat Fragmentation

An American red squirrel. Credit: Gettyimages/iStockphoto

Let’s talk about tree squirrels. More precisely, their habitats.

Tree squirrels are widely distributed across the globe and like to live in wooded areas. As their name suggests, tree squirrels are dependent on trees for food and habitat, often making a leaf nest or living in cavities of trees.

One of the biggest problems tree squirrels face is habitat fragmentation. Habitat fragmentation happens when a habitat gets broken up into smaller disconnected pieces. Sometimes this happens naturally but is usually caused by human activity. Fragmentation can cut individuals or population off from resources in their habitat, and from other organisms, even when quality habitat is available (North Carolina Wildlife Resources Commission).

Photo by Georg Gerster

Here’s an example. You’re a squirrel living in the southern part of a forest, and you often go to the northern part of the forest to because there is more available food and available mates. Some roads and houses get built that block off your access to the other parts of the forest. Now you no longer have access to that source of food and mates. What do you do? Stay where you are, or try to move? Trying to cross a road may be the last time you do it, so choose carefully.

One of the largest problems associated with habitat fragmentation is a loss of genetic diversity. Let’s look at a study done on red squirrels. Loss of genetic diversity can reduce the chances of survival for isolated populations and influence population dynamics (Wauters, 1994). Maintaining genetic diversity is difficult for isolated populations; genetic diversity is still lost when at least one individual joins an isolated population every year (Wauters). However, measuring immigration rate is not always easy. It can be difficult to distinguish between residents and immigrants, and the immigration rate is responsible for genetic diversity in isolated populations, not population size (Wauters).

Squirrels have a very important role in their habitats. They have a habit of taking seeds, burying them, and forgetting where they are. By inadvertently planting seeds, over time squirrels can expand a forest and change the plant composition (Grenrock, 2018). Fragmentation is not just bad for animal populations, but it can affect plant communities over time as well without that method of dispersal.



“Fox Squirrel –” Fox Squirrel, North Carolina Wildlife Resources Commission ,2017.

Grenrock, Samantha. “Why Should You Love Squirrels? Here Are Six Reasons.” University of Florida News , 17 Jan. 2018.

Wauters, Luc A., et al. “The Effects of Habitat Fragmentation on Demography and on the Loss of Genetic Variation in the Red Squirrel.” Proceedings of the Royal Society of London. Series B: Biological Sciences, 22 Feb. 1994.

Image 1 Credit: Gettyimages/iStockphoto

Image 2 Credit: Georg Gerster Aerial Photography

Ohio’s Newest Vector

As we transition into spring arthropods are starting to make an appearance on humans, domestic pets, and wildlife again. Make sure to keep your eyes peeled for the newest vector of disease infiltrating Ohio, the Asian Longhorned Tick!

Divorce in Black-browed Albatrosses

Two black-browed albatrosses. Photo taken by Francesco Ventura. Retrieved from Mclure, 2021: 

Black-browed albatrosses are monogamous birds that typically mate for life. These birds will spend a large portion of the year flying across the ocean and return to land for reproduction with their partner (Aridi, 2021). However, albatross divorce does occur and typically happens when the partners fail to reproduce. Unfortunately, as climate change has increased, so has the divorce rates among the black-browed albatrosses (McClure, 2021).

As global temperature increases with climate change, so does the temperature of the water. The warmer water temperature means a lower fish survival, which means that the albatross will have less food. The albatross will then have to travel farther to get food, thus spending more time and energy out at sea (McClure, 2021). The lower amount of food causes a less successful reproduction rate. The stress from searching farther for food creates the production of corticosterone, a stress hormone secreted in response to environmental triggers (Ventura et al., 2021).

Stress hormones are a big factor in the selection of mates for the reproduction process. Albatrosses produce one chick during the breeding season, so having the correct partner is vital for their reproduction (Aridi, 2021). When albatross spend more time searching to food, they can return late in the breeding season and in poorer health. This is likely to result in less successful breeding and more production of stress hormones (McClure, 2021). Female albatrosses have the ability to sense their physiological stress and mistakenly blame their stress on the performance of their male partner. Due to this partner blaming, the female albatross will sometimes divorce the male and search for a new mate (McClure, 2021).

A study by Ventura et al. (2021) found divorce rates average 3.7 percent. However, divorce rates reach 7.7 percent in 2017 when the highest the surface water temperature was observed. This means that albatrosses respond to higher water temperature by creating more stress hormones, which causes stress in relationships and leads to divorce. The black-browed albatross is a near threatened species, so climate change caused warming water increases divorce and makes the species more susceptible to population loss (Aridi, 2021).


  1. Ventura F, Granadeiro JP, Lukacs PM, Kuepfer A, Catry P. (2021) Environmental variability directly affects the prevalence of divorce in monogamous albatrosses. R. Soc. B. 288:20211212
  2. Aridi R. (2021) Albatrosses Mate for Life, but Climate Change Has Doubled Their ‘Divorce’ Rates. 
  3. McClure T. (2021) Climate crisis pushes albatross ‘divorce’ rates higher – study.

American Pika population on the decline due to climate change

“American Pika” by NPS Climate Change Response is marked with CC PDM 1.0. To view the terms, visit

American Pika’s are a small, generalist herbivores that live on high elevation mountains west of the Rocky Mountains, ranging from Montana down to Utah. Today there are fewer than 1,000 that exist worldwide and with such a low population they are still not under the Endangered Species Act (  The typical habitat climate for an American Pika are cool and moist conditions that rarely go over freezing temperatures and if exposed to temperatures in the 70’s it can be detrimental and fatal (

American Pika’s are sentinel species, meaning they are used to detect risks to humans by giving an advance warning of danger that is to come.  Most of the time humans use sentinel organisms to judge when a pollutant has become an issue because they are able accumulate a pollutant in their body without adverse effects. However, the reason we are watching American Pika is to detect ecological effects of climate change (Wilkening et al., 2013).

There is a major anthropogenic cause destroying the entire population of the American Pika and that is climate change. Climate change is due to the release of carbon dioxide and other greenhouse gasses that become trapped in the atmosphere and degrades our planets ozone layer. Climate change leads to an increase in global temperature, change in weather patterns, and more severe storms. With how sensitive American Pika’s are to temperature changes the slightest increase in temperature can lead to damaging physiological effects within their bodies. To combat this increase in temperatures over the past decade we have seen their range rise by 150 meters (492 feet) in the Great Basin over the past decade (Wilkening et al., 2013).

A shift in the environment that they inhabit can produce multiple stressors that can have cascading effects within their bodies.  When exposed to stressors the body releases glucocorticoids through a three-step process. Glucocorticoids sound scary, but really it is just a hormone that is associated with stress and can have a major impact on the body. The goal of glucocorticoid is to help the animal deal with the stressor they are encountering and bring their body back to equilibrium. By doing this the body shuts down and reduces multiple systems within in order to have access to the maximum amount of energy it can.

From glucocorticoids testing through fecal matter researchers have seen that American Pika’s have been releasing GCs in short burst, which increases their change of survival as well as helps them bring their bodies back to an equilibrium state (Wilkening et al., 2013). When an animal is exposed to a stressor for an extended period it can lead to chronic stress within the animal creating a long-term excretion of glucocorticoid. With a long-term excretion of glucocorticoid their bodies won’t be able to reach equilibrium and as glucocorticoids are being release their immune system will be weakened making them more susceptible to diseases.



O’Mara, C. (2021). American pika. National Wildlife Federation. Retrieved March 22, 2022, from

Sullivan, P. (2022). Natural History (American Pika). Natural history. Retrieved March 22, 2022, from

Wilkening, J. L., Ray, C., & Sweazea, K. L. (2013). Stress hormone concentration in Rocky Mountain populations of the American pika (Ochotona princeps). Conservation Physiology, 1(1).


Anti-Anxiety Medication Increases Boldness in Atlantic Salmon

Timothy Knepp – USFWS National Digital Library

Atlantic salmon (Salmo Salar) are an important indicator of the health of marine ecosystems. Unfortunately, the sensitivity to poor environmental conditions which gives them their status as an “indicator species” also puts Atlantic salmon at risk, with many populations becoming classified as critically endangered, or even locally extinct (Oceana, n.d.).

Certain human activities can be a major problem for Atlantic salmon populations. Chemical pollution is one such issue that can be especially impactful in aquatic environments (Kolpin et al., 2002). Pharmaceutical drugs are particularly concerning, as most wastewater treatment plants are unable to completely remove pharmaceutical chemicals from wastewater (Nikolaou, Meric, and Fatta, 2007).

While pharmaceutical drugs are important for treating humans, livestock, and pets, many can also impact the physiology and behaviors of wild fish. Research on Atlantic salmon has shown that drugs found in surface water can disrupt individuals’ normal neural and endocrine system function (Hellstrom et al., 2016; Klaminder et al., 2019).

Oxazepam, a benzodiazepine drug used to treat anxiety disorders, is one drug that is found in many river systems (Hellstrom et al., 2016; Klaminder et al., 2019).  Oxazepam works by binding to GABA receptors in the body and changing the conformation of the receptors to allow GABA to bind more readily (Singh and Abdijadid, n.d.). GABA is a brain chemical that, when bound to receptors, inhibits brain signals that stimulate activity in the nervous system, so increased GABA binding reduces feelings of anxiety and stress (Singh and Abdijadid, n.d.).

In humans, benzodiazepines produce a sedative-like effect. In Atlantic salmon–as well as other migrating fish–the drug has a counterintuitive effect. Hellstrom et al. (2016) found that Oxazepam increases the rate of migration, and has been considered potentially positive for migration success in certain small-scale, laboratory studies.

So, why does a sedative drug seem to increase activity in salmon? Klaminder et al. (2019) attribute this speediness not to faster swimming, but to increased boldness. They found that Atlantic salmon treated with oxazepam were more likely to fall victim to predators along their migration routes (Klaminder et al., 2019). In other words, increased GABA binding induced by anti-anxiety medications can decrease predation risk perception in Atlantic salmon.

In an already vulnerable species, an increase in the chance of a fatal encounter with a predator can be a big deal–but are Oxazepam loads in rivers high enough to make Atlantic salmon bolder? Probably not (yet)–Klaminder et al. (2019) treated the fish in their study with a much higher dose than is currently found in waterways, and the authors suggest that their findings are not relevant to current pollution levels. But as drug manufacturing and prescriptions continue to increase, it’s important to consider how pharmaceutical pollution levels might increase in the coming years.

In the case of medication, there’s not a simple solution. Unlike other household products that contaminate waterways, reduced usage isn’t always an option. Instead, we need to focus on properly treating wastewater and increasing regulations of pharmaceuticals to prevent them from entering our waterways.

To learn more about how pharmaceuticals are regulated and treated in waterways, visit



Hellstrom, G, Klaminder, J, Finn, F, Persson, L, Alanara, A, Jonsson, M, Fick, J, & Brodin, T (2016) GABAergic anxiolytic drug in water increases migration behavior in salmon. Nat Commun 7. doi:10.1038/ncomms13460


Kolpin, DW, Furlong, ET, Meyer, MT, Thurman, EM, Zaugg, SD, Barber, LB, & Buxton, HT (2002) Pharmaceuticals, hormones, and other organic wastewater contaminants in US streams 1999–2000: a national reconnaissance. Environ Sci Technol 36(6): 1202-1211. doi:10.1021/es011055j
Klaminder, J, Jonsson, M, Leander, J, Fahlman, J, Brodin, T, Fick, J, & Hellstrom, G (2019) Less anxious salmon smolt become easy prey during downstream migration. Sci Total Environ 687(15):488-493.
Nikolaou, A, Meric, S & Fatta, D (2007) Occurrence patterns of pharmaceuticals in water and wastewater environments. Anal Bioanal Chem 387: 1225–1234 (2007). doi:10.1007/s00216-006-1035-8
Oceana (n.d.) Atlantic Salmon. Retrieved March 6, 2022.
Singh R & Abdijadid S (n.d.) Oxazepam. StatPearls [Internet].
Image credit:

Fragmentation impact on salamander

I attended a conference activity called Ohio Natural History Conference last weekend and all posters and presentations are super interesting. Among these excellent presentations, one presentation about salamander habitat and population dynamics attracted my attention. The speaker, Dr. Mike Benard, is from Case Western Reserve University and one of the researches his team did was to investigate population dynamics of salamanders under the modification of their habitats, such as habitat loss and new habitat construction. The talk was great and it also invoked me of how fragmented habitats, which means separate habitats, impact salamanders’ reproduction.

Salamanders of Spring | Lake Metroparks

In the presentation, Dr. Benard and his team sampled the population around a wetland where about 75% of the wetland was removed for the construction of a new sewage plant. I expected that the population of salamanders would decrease due to loss of habitat and limited carrying capacity, which means maximum numbers of individuals can be held in one place. However, in contrast, the population of salamanders increased after a slight decrease due to unknown reasons, which represents that the salamanders gave more births within less habitat (Benard 2022).

On the other hand, the abundance of salamanders was estimated in another area that had a history of agriculture and forest fragmentation. These places were altered artificially after agriculture, including less vegetation and less canopy cover existing. Measured the population of local salamanders, the team found out that the abundance here was quite low (Cosentino & Brubaker 2018). The results reflected that vegetation has a negative relationship with the population of salamanders and forest fragmentation could decrease the reproduction of salamanders (Cosentino & Brubaker 2018).

In addition, calculating the risk of local extinction of salamanders, assuming a population isolated from breeding grounds, was used to assess the possible impact of habitat fragmentation in salamanders’ survival. The parameters were calculated using data from the previous 18 years. Their findings revealed a high likelihood of local extinction of the population under habitat fragmentation. It highlighted the grave repercussions of fragmentation (Bar-David et al. 2007). As a result, terrestrial habitats must be protected, and landscape connectivity must be promoted to allow individuals to migrate between breeding locations for potential escape benefits.

In conclusion, the fragmented habitat has various impacts on the population dynamics of salamanders. For example, low vegetation cover would result in low reproduction rates(Cosentino & Brubaker 2018). And isolated populations could show a negative relationship with salamanders’ survivals(Bar-David et al. 2007). The restoration and protection of habitats and connected populations are necessary.





Bar-David, Shirli, Ori Segev, Nir Peleg, Naomi Hill, Alan R. Templeton, Cheryl B. Schultz, and Leon Blaustein. Long-Distance Movements by Fire Salamanders (Salamandra Infraimmaculata) and Implications for Habitat Fragmentation. Israel Journal of Ecology and Evolution 53.2:143-159 (2007).

Benard, M. Ambystoma salamander population dynamics during 11 years of habitat modification and restoration. Ohio Natural History Conference (2022).

Cosentino, B.J., Brubaker, K.M. Effects of land use legacies and habitat fragmentation on salamander abundance. Landscape Ecology 33, 1573–1584 (2018).



A Shad Day at the Hoover Reservoir

A couple of weeks ago, I was driving around with my dog and decided to stop at the Hoover Reservoir to take a quick walk. As my dog and I approached the edge of the water, I quickly noticed dozens of little silver fish floating on the surface (pictured below). I initially assumed all of the fish were dead, but after some observation I noticed that some were still trying to swim (rather unsuccessfully). I was taken aback by the number of fish that were either already dead or well on their way there, and I began to wonder what kind of fish they were and why this was happening.

After trying to remember all of the fish I learned in my taxonomy class last semester, I guessed that the fish in question were Gizzard Shad (Dorosoma cepedianum), which I later confirmed with a google search. I then made a few searches to see if something like this has happened before, and quickly found that Gizzard Shad are very sensitive to cold weather and die-offs like these happen relatively often with this species. In fact, it has been noted to be a normal annual occurrence in spring for some areas (Muzyk, 2022). 

Studies have shown that Gizzard Shad are often susceptible to starvation over the winter, as they cannot take in nutrients as efficiently in cold water. For smaller fish, these energy reserves are even smaller and result in them being more sensitive to and dying much quicker in colder waters (Fetzer et al., 2011). This explains why all of the fish I saw were relatively the same size (less than 3 inches). This spring die-off, while it may be s(h)ad to see, is a part of the life history of this species and is a normal occurrence that plays into their population dynamics.


Gackenbach 2022


Fetzer, W. W., Brooking, T. E., Jackson, J. R., & Rudstam, L. G. (2011). Overwinter mortality of gizzard shad: Evaluation of starvation and cold temperature stress. Transactions of the American Fisheries Society, 140(6), 1460–1471.

Muzyk, C. (2022, February 15). Nothing’s fishy: Gizzard shad die-off at Lake Brittle is a common, natural occurrence. Prince William Times. Retrieved March 7, 2022, from


Photographs by Madelene Gackenbach (2022)

Human Activity Continues to Threaten a Federally Listed Snake

The eastern indigo snake (Photo 1), Drymarchon couperi, is a large, nonvenomous snake native to southeastern coastal plain areas, most commonly in southeastern Georgia and peninsular Florida. The species was federally listed as threatened in 1978 and has been the focus of recent conservation efforts. These snakes are long-lived and reach sexual maturity relatively late at 3-4 years of age (Hyslop et al. 2012).

Photo 1: An eastern indigo snake in Florida; photo originally taken by Todd Pierson and made available via the Florida Museum: Florida Snake ID Guide. Link:

The eastern indigo snake has primarily been threatened by habitat fragmentation and degradation, as seen by the fact that the longleaf pine and wiregrass sandhills that these snakes reside in have faced an area decline of over 97% since European colonization (Hyslop et al. 2012). and Breininger et al. found that over 50% of known eastern indigo snake mortalities within their 2012 study were due to human activity along roadways. The eastern indigo snake’s size means it is rarely preyed upon, so roads and human activities are a common source of mortality for this species (Breininger et al. 2012).

Figure 1: The top figure shows the annual survivability of the eastern indigo snake in three different areas (conservation core, conservation near roadway, and suburb) and the bottom figure shows the probability of encountering an eastern indigo snake in the same three areas. Figure courtesy of Breininger et al., 2012.

Beyond the increase threat to the survival of this snake due to roadways, urbanization is causing the home range to become increasingly restricted. Their northern range had previously been limited in part due to their use of Gopher Tortoise burrows as a source of protection from weather events and predators or as a breeding and nesting site (Hyslop et al. 2012). In more recent years, increased urbanization has led to a decrease in habitat diversity and home range size. In response to habitat fragmentation, it is very common to see animals increase their home range size, however eastern indigo snakes have had the opposite reaction. The mean area used by this species has decreased and the reason behind the change is still unclear. The leading hypotheses are that the snakes in suburbs moved less because they were easily able to find prey, the snakes outside of the suburbs have purposefully decreased their range and altered behavior in order to avoid roadways, or that the eastern indigo’s ability to take over den sites and feed on a wide variety of prey has allowed the snake to occupy areas uninhabitable to other species (Breininger et al. 2011). The exact reasoning for the alterations in the eastern indigo snake’s behavior and home range may be unknown, but all current hypotheses have important conservation implications and work is continuing to be done to ensure the survival of this species.


Breininger, D. R., M. J. Mazerolle, M. R. Bolt, M. L. Legare, J. H.Drese, and J. E. Hines, 2012. Habitat fragmentation effects on annual survival of the federally protected eastern indigo snake. Animal Conservation 15: 361-368.

Breininger, D. R., M. R. Bolt, M. L. Legare, J. H.Drese, and E. D. Stolen. 2011. Factors influencing home-range sizes of eastern indigo snakes in central Florida. Journal of Herpetology 45: 484-490.

Hyslop, N. L., D. J. Stevenson, J. N. Macy, L. D. Carlile, C. L. Jenkins, J. A. Hostetler, and M. K. Oli. 2012. Survival and population growth of a long-lived threatened snake species, Drymarchon couperi (Eastern Indigo Snake). Population Ecology 54: 145-156.

Pearson, T.,  2021. Eastern Indigo Snake. Florida Museum of Natural History.

The Mauritius kestrel is adjusting its phenology according to temperature changes

Photo credit: Willard Heck, retrieved from The Peregrine Fund,

As global temperatures warm, many species must make adjustments to their range or the timing of life-history events in order to continue to survive and reproduce in a changing world. Some species are considered more vulnerable to these changes, including species native only to islands because their limited range increases the risk to populations from climate events and they have a limited ability to disperse (Taylor et al. 2021). This greatly limits their capacity to adapt to climate change by relocating to a more suitable location with favorable conditions. As such, the only likely way to adapt to climate change for many island-endemic species is through phenotypic plasticity, by which animals alter the timing of life-history events such as reproduction (Taylor et al. 2021).

One such species is the Mauritius kestrel (Falco punctatus). This small bird of prey, native only to the small island of Mauritius in the Indian Ocean, was once the most endangered bird of prey in the world, with a population in the 1970s consisting of only two known breeding pairs, causing a genetic bottleneck where the existing gene pool was extremely limited (Jones et al. 1995). Thanks to repopulation efforts over several decades, the Mauritius kestrel made an incredible recovery and population estimates indicate there are now over 800 individuals (Jones et al. 1995). These birds of prey breed beginning in the dry spring, raising their young as the warm rainy season begins in the early summer (Taylor et al. 2021). But climate change could drastically alter seasonal patterns in Mauritius and put wild populations at risk of declining once more.

A new study published in 2021, however, shows that Mauritius kestrels may have a better chance of adapting to climate change than previously believed. Taylor et al. (2021) tracked rainfall patterns and breeding phenology of Mauritius kestrels between 1962 and 2016, along with other measures of breeding success. Between 1994 and 2014, the study found that the first egg-laying date advanced by about 0.7 days per year, influenced primarily by the mean temperature in the three-month period of July-September (Taylor et al. 2021). Additionally, Taylor et al. (2021) found that overlap of the rainy season with the breeding period had a negative impact on breeding success, favoring earlier breeding. Despite having experienced near-total extinction and an extremely limited gene pool, the population has retained phenological responses that are sufficient for it to track these environmental changes and adapt (Taylor et al. 2021). The Mauritius kestrel demonstrates phenotypic plasticity by adjusting its breeding period as temperatures increase, which may allow it to better adapt to changing environmental conditions despite being an island species that are considered to be more vulnerable to these same changes.


Taylor J, Nicoll MAC, Black E, Wainwright CM, Jones CG, Tatayah V, Vidale PL and Norris K. (2021). Phenological tracking of a seasonal climate window in a recovering tropical island bird species. Climatic Change 164:n.p.

Jones CG, Heck W, Lewis RE, Mungroo Y, Slade G and Cade T. (1995). The restoration of the Mauritius Kestrel Falco punctatus population. IBIS 137:173-180.

The Peregrine Fund. (n.d.). Mauritius Kestrel. Retrieved 5 March 2022 from