Prothonotary Warbler

Prothonotary Warbler

Wednesday, 16 March 2016

Endangered species habitat

Several weeks ago, I posted a few blogs about Pelee Island, including one post that dealt specifically with some of the endangered snakes. You can read about it here. 

With all of the development that has taken place on Pelee Island and is proposed to take place, some of the critical habitat elements that snakes require are at risk, placing these already endangered snakes at further risk. There are options, however, which may reduce further risk:
  • one option is to buy up the island and convert it back to its natural habitat (believe it or not, that was an option that was bandied about several decades ago! It didn't get too far, not surprisingly);
  • another option is to acquire some of the best remaining pieces of natural area and if possible, connect the pieces so that the snakes have a safe travel corridor along which to go to and fro; 
While acquisition of habitat, or creation of habitat might be done specifically for the benefit of these endangered snakes, in the bigger picture there may be lots of other species, some rare and some not so rare, which will be much better off as well.

If habitat is to be protected, it may be necessary to create features on it that would serve the snakes well for some critical aspects of their life cycle. There have been various efforts to create what I refer to as Critical Habitat Element Clusters (CHEC) on Pelee Island, and include:
  • Hibernacula
  • Egg-laying sites
  • Basking hot rocks
  • Brush piles
Ideally, if these CHEC are available in such proximity so that the snakes don't have to travel a long way and risk their lives crossing roads, it will save their energy and keep a lot more of them alive.

Hibernacula
Snakes are cold-blooded, and spend a good part of their lives underground, below the frost line. There are various ways to create hibernacula, but here are the basics of how we did it on Pelee Island.

A backhoe was used to dig a hole almost two metres deep.
We got large rocks to put at the bottom of the pit....the larger the better.
 The intent was that the rocks are large enough so that there would be numerous cavities at the bottom. We then placed 3 or 4 long plastic pipes (about 4"-6" diameter) leading to various cavities.
 Progressively smaller sized rock was placed on top, being careful not to damage the pipes. The smaller and smaller rock will prevent the uppermost layers of material from falling through, leaving the largest cavities at the bottom.

Fibre cloth matting was placed on top.
The top layer was fine gravel screenings.
The fine screenings at the top will become quite hard, and limit the amount of vegetative growth on the top. This exposed surface serves as a basking site when the snakes are just about to go underground in the fall, or when they begin to emerge during the first warm days of spring.
 Having several access points allows for safety: if for some reason one pipe gets plugged or collapses, there are still others to enter or emerge through.


Basking Hot Rocks
Being cold-blooded, snakes rely on the warmth of sunlight to maintain or increase their physiological activity. For females that are developing eggs inside of them, proper physiological processes are critical for them to be able to lay their eggs early enough, so the young will develop in enough time so that they can hatch early enough in the summer to be able to grow a bit before finding a place to hibernate for the winter. Timing is everything!

The top of the hibernacula can be useful for basking, as mentioned, but one can create other basking sites as well. It is important to have the basking surfaces in layers. And being elevated, it increases the time that the sun is available for basking.

First, place some blocks on the ground in an open area with lots of sun.

In our case, we had pieces of an old concrete slab available, which were perfect for our needs. By creating layers, it gives a basking snake options to choose the right exposure and temperature to its liking. If it feels threatened, it can quickly escape to a more protected part of the hot rock cluster.

Another version of basking hot rocks

Egg-laying site
Both the endangered Blue Racer and Eastern Fox Snake lay eggs. They seek out a pile of decomposing material that they consider to have the right sunlight exposure and moisture so that the eggs, once laid, will have the benefit of warmth and humidity to maximize the chances of the young being able to hatch successfully. In a totally natural setting, this could be an opening in a decomposing log. But where logs are unavailable, snakes have been known to use piles of straw, manure, or wood chips. Creating a suitable egg-laying site is really quite simple: find an open sunny area and dump a large pile of wood chips!


 Such a pile may not be suitable right at the outset, but it will gradually decompose, holding moisture and the snakes can use these piles for several years.

Brush Piles
Snakes shed their skin several times a year. During this period, their eyes cloud over as they "go into the blind". They are much more vulnerable at this time, so they seek out areas where they can hide safely for several days, until the skin is shed. Suitable sites for this period could include a brush pile. Since Pelee Island has a lot of grape growing operations, there are lots of old grape stalks being culled from the vineyards. They are robust, and should last for many years. The material was free for the asking.
 Of course one can just use good old brush and branches as well.
These brush piles may also serve as communal gathering places, where courtship and mating will take place.

As mentioned earlier, having these CHEC in close proximity will minimize the need for the snakes to travel far and wide to seek the habitat they require. This next image shows a brush pile, egg-laying pile and a hibernaculum all within sight. The basking hot rocks are just around the corner. All four of these Critical Habitat Elements are important. Just as a chain is only as strong as its weakest link, if any one of these CHE are not available, the survival of the population of Blue Racer and Eastern Fox Snake on Pelee Island is at risk.
We were able to create 7 of these CHEC all strategically placed in some moderate habitat that wasn't available to these endangered species before. Now this moderate habitat has become excellent habitat!








6 comments:

  1. Oh my Allen, what wonderful ideas for these threatened snakes. How wonderful that some people care enough.
    Love and blessings, Paula.

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    1. Hi Paula. Thanks for your visit and comment.....yes, snakes sure aren't universally loved, but their place in the ecosystem is important and fortunately there is a lot of effort being put forth by some, to ensure their survival.

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  2. What fascinating ideas, and so practical! I had no idea these simple ideas would be so beneficial. Glad to know the original Stone Road Alvar we worked on is getting such extra attention.

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    1. Hi Stew.....it has been such a loooong time! Thanks for your visit and comment. Things on Pelee Island have definitely improved in many respects over the past few decades, but those concerned with the natural environment there have to remain vigilant,

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  3. Hi Allen, How has your snake hibernaculum worked out? Have snakes been using it? How do the snakes travel through the pipes? Are they not too slippery, esp. on the way out? Would you modify the design any way?

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    1. Good question, and I wish I could give you some definite answer! This all happened before I retired, and I recommended some monitoring follow-up, but as far as I am aware, no monitoring ever took place. Because most of the target species are habitual and once they have a safe hibernaculum, it is most likely that snakes displaced from other hiberacula or 'new' individuals dispersing from another area and encountering these features would be the ones most likely to make use of them. Therefore it could be several years before the target species might show up. Monitoring, as useful as it would be, would not be all that easy as an enclosed drift fence would have to be installed in the early spring, and then checked at least a couple of times a day for possibly several weeks to ensure any snakes trying to exit the hibernacula were not prevented from doing so.

      As for the design: I don't think the snakes would have any trouble entering or exiting the pipe. They have the ability to use their body to brace themselves quite effectively to enable easy movement.

      There are variations of this overall design, just as in a purely natural situation, the snakes would utilize hibernacula of various styles. In constructing one like we did, a lot depended on the site characteristics, the materials available and the person-power or equipment to build it. We were fortunate in having the equipment and materials to do it on this large scale with relative ease.

      Thanks for asking and I hope this helps a bit.

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