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The science behind eyeshine

 

Here in the northern hemisphere, the autumn days are getting shorter and shorter. It’s getting darker earlier in the day, and our eyes have to adjust to dim conditions.

Without the help of fire or electric lights, we humans are pretty bad at night vision. Unlike many other animals, our eyes lack a specialized reflective surface that aids sight at night and in low light environments (caves, under water, etc.). This surface, called a tapetum lucidum, located behind the retina, acts as a mirror to reflect light photons.

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Humans lack the tapetum lucidum located in between the retina and choroid in the eyes of many nocturnal animals (Source).

Light enters the eye and hits photo receptors in the retina. Some light, however, will miss the photo receptors and pass past the retina. The tapetum lucidum reflects that light and gives it a second chance to hit the photo receptors and illuminate the scene.

Some of this light is reflected back out of the eye, which is why some animals’ eyes appear to glow in nighttime trail camera photos.  All types of camera flash, even the low-glow infrared flash of the Snapshot Wisconsin cameras, can reflect off the tapetum lucidum and cause an animal’s eyes to light up. (This is not the same as the red-eye effect seen in photos of human eyes which is caused by light reflecting off the blood vessel-rich choroid behind the retina.)

There is variation in mineral content and structure of the tapetum lucidum, which causes eyeshine in different species – and even different breeds of dog – to look different. Eyeshine may appear white, blue, green, yellow, pink or red.  It’s too bad nighttime trail cam photos are in black and white and we can’t see these color differences!

Animals having a tapetum lucidum (not extensive):

  • deer
  • carnivores: canids and felids
  • grazing animals: sheep, goats, cattle, horses
  • ferrets
  • lemurs
  • marsupials
  • fruit bats
  • ray-finned fishes and cartilaginous fishes including sharks
  • owls and a few other nocturnal birds
  • crocodilians including alligators (bright red eyeshine – spooky!)

Animals lacking a tapetum lucidum (not extensive):

  • higher apes including humans
  • kangaroos
  • pigs
  • squirrels*

*I’ve read that squirrels don’t have a well developed tapetum,  but flying squirrel eyes certainly glow in our nighttime trail cam photos. Anyone who can shed some light on this mystery, please leave a note in the comments!

 

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Sources:

 

 

 

 

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Vivek’s citizen science and camera trapping experiences

In this post, I’ll be talking a little bit about my experiences with citizen science and camera trapping projects prior to joining Snapshot Wisconsin.

Before I decided to become a wildlife conservation professional, I was involved with citizen science projects as a volunteer. I found pleasure in natural history, making observations and collecting data for scientists. This was my contribution to saving the world, I thought! As a volunteer, I have done large mammal surveys in India, from counting tiger prey species to collecting carnivore scat. I learned a lot from participating in these projects. More than anything else, I think they provided a welcome distraction from my day job as a software programmer *chuckle*.

Here’s a misty morning scene from Nagarhole National Park, while I waited for the survey start time of 6 am.

I was also involved with conservation groups in the Western Ghats landscape of India. One project I am proud of being associated with is the Bisle Frog Watch. Every year citizen scientists congregate at Bisle (a tiny village in the Western Ghats) to learn about amphibian ecology and identify them in the wild under the guidance of researchers. What is heartening is that over a period of 6 years, we have made a checklist of 36 species of amphibians!

A night time frog watching field visit in progress.

A regular feature of our frog watch: a winged gliding frog( Rhacophorus lateralis) perched on a rock.

Apart from mammals and amphibians, I also love bird watching and regularly submit my bird lists to eBird.

A whimbrel from the Western coast of India.

Some of these experiences with citizen science gave me the confidence that I too can do scientific research. And, that’s also how I decided to pursue a Master’s degree.

Talking about my camera trapping experiences, I worked on a trail camera survey in Ecuador for my Master’s capstone project. I worked with an Ecuador based non-profit called Ceiba Foundation for Tropical Conservation. We set up a total of 16 camera traps on several private properties and nature reserves in the Manabi province of coastal Ecuador.

Whereas the most common species in Snapshot Wisconsin is the white-tailed deer, in my project in Ecuador it was the agouti. (Although white-tailed deer have been recorded in the study site in Ecuador, they are uncommon in those parts of the world.) Whereas in Snapshot Wisconsin we see bobcats, in Ecuador we frequently recorded wild cats like ocelot, margay and jaguarundi.

In fact, I am even leaving an identification challenge for some pictures from Ecuador. Feel free to leave your guesses( along with the picture number) in the comments below. I shall post the answers soon-ish!

Jaguarundi

Picture #1

Margay

Picture #2

Ocelot

Picture #3

Tayra

Picture #4

All in all, it is exciting to be working on the Snapshot Wisconsin project – with the many citizen scientists who host camera traps across Wisconsin and many others from around the world classifying pictures – knowing we have something in common.

 

Picture credits: Frog watch pictures – Deepika Prasad; Camera trap pictures from Ecuador – Ceiba Foundation for Tropical Conservation.

September #SuperSnap

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This month’s #SuperSnap comes to us from CraftyWench.  This turkey was captured flapping its wings while perched in front of an educator camera in Sheboygan County.

Check out all the nominations by searching “#SuperSnap” in Talk. Hashtag your favorite photos for a chance to be featured in the next #SuperSnap blog post.

Elk Rut Happening Now!

The elk rut peaks mid-September to mid-October. A Wisconsin resident recently caught an amazing video of bull elk getting rowdy in preparation, which you can see if you visit this link.ElkVideoScreenshot

Our trail camera hosts in the elk reintroduction areas – Black River Falls, Clam Lake and Flambeau River State Forest – have been checking their cameras and uploading photos.  We rely on these camera checks to gather data on how the elk are doing in Wisconsin and to get great photos to share!

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Bugle Days participants

Bugle Days is an annual tradition held in Clam Lake Wisconsin by the Wisconsin Chapter of the Rocky Mountain Elk Foundation.  Snapshot Wisconsin was invited to participate this year in order to share some info about our elk monitoring project, recognize current volunteers, and recruit some new volunteers.

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Elk Monitoring Volunteers!

Bugle Days presented a great opportunity to see some of our volunteers who we haven’t seen since training, and also to get out in the field during the day and check some cameras.  We ended each evening with a slide show of Snapshot Wisconsin images accompanied by a campfire.

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Snapshot Wisconsin Slide Show

We are currently looking for more trail camera hosts in each elk range area.  These cameras are set up on public land so all volunteers need to participate is transportation to the camera areas, a handheld GPS device, and a healthy sense of adventure!  To find out more information about the elk monitoring opportunity send an email to DNRSnapshotWisconsin@Wisconsin.gov with the subject line “Elk Monitoring”.

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Trail to one of the Clam Lake elk cameras

 

August #SuperSnap

This month’s #SuperSnap comes to us from @Snowdigger.  Although we’re still enjoying the late summer here in Wisconsin, we couldn’t resist sharing this snowy winter scene featuring a coyote.  There are also signs of another critter who occupies this wood; look closely to see trees that have been felled by beaver.

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Check out all the nominations by searching “#SuperSnap” in Talk. Hashtag your favorite photos for a chance to be featured in the next #SuperSnap blog post.

Science update: Fisher distribution

Our July #SuperSnap was all about fishers, and we’re just going to keep on rolling on the fisher train! This science update was inspired by recent comments on a photo of a fisher in central Wisconsin. The location of the photo might cause confusion if you base where fishers *should* be on the range map we have posted. The map shows fisher range extending to only the very northern part of the state:

FisherMap.jpg

Whereas we’ve seen fishers on Snapshot Wisconsin cameras in counties pretty far south:

Fisher.jpg

In the case of a species like fisher, which was reintroduced to Wisconsin in the 1950s and expanded its range quickly, static distribution maps go out of date quickly. This brings up a larger point about range maps being inaccurate because they are based on old, incomplete or faulty data. We provide range maps to give volunteers an indication of where they are more likely to find a certain species, but these maps are by no means perfect. The fact that we do not have very good statewide data on the distribution of most species is indeed a major reason for starting a project like Snapshot Wisconsin!

Note that the above map shows counties where we’ve seen Snapshot Wisconsin photos correctly classified as fisher. Many of the gray counties do not have any Snapshot Wisconsin cameras and so we do not have any photos there yet. This is not to say there are no fishers in the gray counties!

July #SuperSnap

This month’s #SuperSnap selection goes to this agile fisher nominated by @Snowdigger:

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Fishers (Martes pennanti) are medium sized mustelids with slinky-like bodies and dark fur. Despite the name, fishers seldom eat fish. Instead, their diets consist of small mammals, and are one of a handful of animals capable of preying on porcupines. Fishers were reintroduced to Wisconsin in the 1950s, and have done well in the state since then – so well, in fact, that Wisconsin fishers have been re-located for reintroduction efforts in other states.

#SuperSnap is a monthly blog feature and a way for us to share some of the best Snapshot Wisconsin photos! Hashtag your favorite photos for a chance to be featured in the next #SuperSnap blog post, and check out all the nominations by searching “#SuperSnap” in Talk.

How does NASA play into Snapshot Wisconsin?

Astute contributors to Snapshot Wisconsin may have noted that one of the primary partners on the project is NASA. Yes, that NASA, known for space-flights and Neil Armstrong. For many people, the involvement of an air and space agency with a wildlife monitoring project may not be intuitive. Here’s how NASA and Snapshot Wisconsin work together:

NASA doesn’t just focus on our sun, solar system, and broader universe. It also has a dedicated Earth Science branch that houses research related to our atmosphere, weather, energy cycling, and ecosystems. ThisNASA-Earth-sciences branch aims to predict change over time in, for example, energy cycling or biodiversity resources.

 

Some things, like animal population processes, are incredibly difficult to track across large spatial areas. Even with all the Snapshot Wisconsin cameras out on the ground, the total physical area in which we are observing animals is fairly limited – a point where each camera is, with a lot of space in between points. What we need to do is fill in the data gaps between camera locations. In other words, we need to be able to make predictions about areas where we don’t have observations. And this is where NASA comes into play.

NASA maintains a number of satellites that orbit Earth. These satellites carry on-board sensors that record light reflectance off of the Earth’s surface at different wavelengths. The images these satellites take of the Earth’s surface can be used to determine, for example, the locations of different landcover types (forest, wetland, prairie, etc.), or where leaves are growing or senescent, or where and when there is snow-cover. What’s great about these sensors is that they take photos regularly, and over large continuous spaces, so we can collect these data from our trail camera locations AND the spaces in between them.

Two of the more important sensors for our research are the Landsat and MODIS sensors. Landsat images have a spatial resolution of 30 meters (think of this as a pixel size – each pixel is 30 m by 30 m) and a temporal resolution (i.e., gap between flyovers) of 16 days. MODIS images have a spatial resolution of 250 – 500 m, and a temporal resolution of 1-2 days. These sensors are complementary—MODIS’s greater temporal resolution makes it more useful for detecting temporal environmental changes like plant green-up, while Landsat’s greater spatial resolution makes it more useful for detailed mapping of relatively static environmental attributes, like the location of forests, wetlands, and prairies.

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Landcover maps of the same area derived from Landsat (left) and MODIS (right) satellite images. Modified from Schmidt et al. 2012.

How do we use satellite data and trail camera data together? We determine the association between the number of animals we count in trail camera photos and a series of environmental variables taken from satellite data. Understanding these associations gives us an idea of why animals might be more or less abundant in some places than in others, and allows us to suggest actions managers might take. For example, we might find that prairie chickens are highly associated with prairies but not with forests, and so we might suggest removing trees that are encroaching upon prairie land  in order to increase prairie chicken numbers.

Without images collected from space, it would be incredibly difficult to reliably predict and map the distribution and abundance of species.

New elk reintroduction

The following post is by a guest blogger, Joe Dittrich,  research scientist at the Wisconsin Department of Natural Resources. Joe was involved in the new elk reintroduction in the Flambeau River State Forest (Sawyer County) and shares the experience here. Thanks Joe!

Read More…

When Programs Intersect

In a previous post we shared an experience on a property restored to prairie with help from a landowner program. Did you know that 55% of Snapshot Wisconsin trail camera hosts participate in landowner programs?  The Wisconsin DNR offers many opportunities for landowners interested in managing their property.  These programs include:

Other programs are available through the University of Wisconsin Extension, including the Wisconsin Coverts Project. This project provides 3-day workshops for landowners who want to learn how to enhance their woodlands for wildlife.

Recently, a Snapshot Wisconsin volunteer in Iowa County shared with us photos captured by her trail camera after she conducted a prescribed burn on her property. Prescribed burns can be used to improve wildlife habitat, control invasive plant species, restore and maintain native plant communities and reduce wildfire potential. The Landowner Incentive Program provided support to carry out the burn.  Shortly after the burn, turkeys started using the area and showed off for the Snapshot Wisconsin camera. We were excited to see these two programs intersect!

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More resources for landowners can be found on the Wisconsin DNR website. Are you involved in any landowner programs?  Tell us about it in the comments!