Thursday, December 27, 2012

Frost crack

What: A few weeks ago, one of the kids at Crow's Path and I found a white ash (note the diamond shaped grooves etched in the bark) that had a strip torn out from the trunk. The missing section was about 6" wide running a cork screw from the base of the tree right up the bole about 30' up. While pondering about how the scar got there, we started looking for the missing chunks. We found the lion's share about 20' away from the tree - chunks of wood with bark still attached. Also visible in the scar is a thin seam running the length of the exposed area.

The tree was dead and has been for some time, while the crack was fresh (it wasn't there three weeks earlier). The majority of the crack ran along the side of the tree facing southwest towards an open field (and the winter sun). We decided that the explosive event must have been due to frost cracking.

Ecological notes: Frost cracking occurs on super sunny days that are also super cold. When the sun was shining down on the white ash, the tree's bark heated up rapidly (like your cat's fur when it lays on the ledge next to the window). As the bark warmed it conducted heat inward and the core of the tree slowly heated as well. Wood's not the greatest conductor of heat, so the process is a slow one.

If the tree happens to be in full exposure it's got lots of time to conduct heat to the inner heartwood. In deeper woods, however, where there are lots of other trees around to shade each other as the sun moves across the sky, the bark cools as quick as it warms and the core is less likely to heat up. You probably well know the difference on a cold day of standing in the sun versus standing in the shade. As soon as you step into a shadow you're hit with the shivers. This whole heating thing isn't necessarily a problem, at least until the tree starts to cool.

As the tree heats up it expands, and when it cools it contracts. As soon as the sun sets or ducks behind another tree, our dead ash began to cool and cool rapidly, starting with the outside, that was only staying warm because it was in the sun. As the bark and outer wood cools (and cools rapidly) it contracts. If the tree cools too fast: kablooey! The tree can literally explode. There's more to it than that, but that's a start.

Recap of how frost cracking occurs:
  1. Tree grows up to be big, with one side exposed to the south
  2. Cold sunny day
  3. Over a long period of time the bark warms, conducts heat to heartwood, which expands
  4. Sun sets/casts a shadow, outer layers of the tree cool very quickly
  5. As it cools it shinks around the expanded inner wood and kablooey!

Conditions conducive to frost cracking:
  1. Larger diameter tree (stores more heat, can expand more)
  2. Cold, sunny day
  3. Dark barked tree (dark colors absorb more heat)
  4. Smooth bark (rough bark, like a radiator, dissipates heat)
  5. Tree growing in open
  6. Defects in wood (doesn't handle contraction nearly as well as healthy wood)

Where: Frost cracking typically occurs on the south, or sun-exposed surface of thinly barked trees. Edges of woods are great places to find this. I see it most often on species where Vermont is at the northern edge of its range (like red oak - I'll post more on the crazy oak inside an oak healing pattern - aka frost ribs - on these trees later this winter).

Saturday, December 22, 2012

Beavers in the Retention Pond (Part VII)

Some great news! UVM has decided to pull the kill traps, at least over the holiday break, expressing also that after break they would return to the issue and re-evaluate other options. There's even the possibility that they'll convene a group from Rubenstein and the community to discuss these other options. Thanks again to everyone for providing support in their own unique way. Alicia keeps reminding me what a complex issue this is, which is why it's so important to have so many voices and perspectives, to remind us of the complexity when we try and control/manage wild things.

And a huge thanks to Katie Flagg, who wrote the 7Days article, for shedding light on this, and acknowledging the complexity. She was on WCAX this week to talk more about her article. I love the end: "The Centennial Woods [Natural] area is really beloved by a lot Burlingtonians. People use it to walk their dogs, they go out there all the time, but there isn't a great way right now for teachers, students, Burlington residents to weigh in on how that area is managed. The beavers themselves are now actually slightly outside of the Centennial area. What everyone would like, and I think UVM and the naturalists have agreed on is better communication about how the land is being managed."
WCAX.COM Local Vermont News, Weather and Sports-

Friday, December 21, 2012

Beavers in the Retention Pond (Part VI)

What: 7Days just published an article about the beaver situation. Thanks to all the people that have gotten in touch with me about ways in which they can help. I was called a "renegade" by one staff at UVM Grounds, which was unfortunate to be labeled a renegade for making public what's happening on public land. Though, I suppose I'd be in alright company. In Thoreau's Civil Disobedience he writes, "But, to speak practically and as a citizen, unlike those who call themselves no-government men, I ask for, not at once no government, but at once a better government. Let every man make known what kind of government would command his respect, and that will be one step toward obtaining it." So for all the people that have gotten in touch with me (from around the country too!!) asking how they might get involved, I encourage you to speak up, to let folks at UVM know what you want to see happen, whether you agree with me, them, both, or none of us. Simply let your voice be heard.

I'd start by reaching out to meEnrique Corredera, who is the director for UVM communications, and Sal Chiarelli, Director of Physical Plant. You can also write letters to the editor to comment on the 7Days article. As Alicia said in the article, this isn't a case about good vs bad. There are cases to be made for many different solutions, so it's important to be strong, but open minded in this; as were Afrika Bambaataa's renegades of funk.

As mentioned in the article the three initial conibear traps were removed by someone walking into an unmarked, retention pond with a gate wide open. In response UVM started locking the gate and put up no trespassing signs to secure the new traps the hired trapper set on the berm between the upper pond and lower pond (I've seen deer on several occasions in the retention pond, though even with gates locked the deer could walk in through one of the other large holes in the fence). So accessing the pond would now be a legal violation (I think this statute covers the possible repercussions, though there may be others as I don't know the legal system).

Last year NPR's Fresh Air had a special celebrating 100 years of Woody Guthrie. They talked about a verse often edited out of "This Land is Your Land":
As I went walking I saw a sign there
And on the sign it said "No Trespassing."
But on the other side it didn't say nothing,
That side was made for you and me.
Other notes: I'd also like to expand on Katie Flagg's use of the word tame in her article. To me that word is less like the domesticated use of it (like kitty-pets in Erin Hunter's Warriors series), and more like the meaning Antoine de Saint-Exupery describes so poetically in his book The Little Prince:
"No," said the little prince. "I am looking for friends. What does that mean-- 'tame'?"
"It is an act too often neglected," said the fox. "It means to establish ties."
"'To establish ties'?"
"Just that," said the fox. "To me, you are still nothing more than a little boy who is just like a hundred thousand other little boys. And I have no need of you. And you, on your part, have no need of me. To you, I am nothing more than a fox like a hundred thousand other foxes. But if you tame me, then we shall need each other. To me, you will be unique in all the world. To you, I shall be unique in all the world..."
"I am beginning to understand," said the little prince. "There is a flower... I think that she has tamed me..."

Wednesday, December 19, 2012

Beavers in the retention pond (Part V)

What: I've just finished editing and touching up my students' entries to the Natural History Dictionary. Took a lot longer than I hoped, but it's certainly worth it. Definitely a work in progress, but I think it's shaping up to be something really really helpful and fascinating!!

So last Friday the kill traps went back up. UVM has killed at least one of the beavers so far, and another one went missing since last Thursday (with finishing up grading I haven't been able to spend as much time out there, so there very well could still be three left, but I was only been able to see/hear 2 last night; all the time spent grading means that this footage is all old). I'm not universally opposed to trapping, I just think in this case it's being done irresponsibly (ecologically and in terms of the community perspective), in a short-sighted way, and as a result of prior ineptitude.

UVM Grounds won't respond to my questions about the process involved or why it's so imperative to kill them - an unfortunate lack of transparency - so I'll speculate based on personal observation and what I've heard second hand. From what I gather the beavers have to go because part of the requirement for managing the retention pond (built as a mitigation for paving the parking lot next to the Centennial Field) includes monitoring and managing for both water quality and water height. Apparently they have to check these every month to meet legal obligations. Water height is an easy one, but I would assume they're either not doing it regularly or doing it poorly as the beavers have been there for 4.5 out of the last 7 months (a 2 month stretch from June to late July, and again from late September until now). Most of that time the water has been about 4' higher than normal.

As for pollution, I don't know how beavers being there would make any difference or what kind of pollution they'd be measuring (biological or chemical). It's not like any of the vegetation is doing any biofiltering of anything this time of year. And the volume of water flowing out should be the same as if the water were 5' lower. Beavers don't really carry rabies and there's never been a rodent-to-human infection, not that that should be a concern (if it was they'd probably want to do something about the raccoon population.

Beaver scat! A rare site! Basically it's just saw dust. This is from Mill Pond 
Humans are far more likely to carry giardia than beavers (beaver fever's a misnomer - most birds and mammals can carry the parasite, and people get giardia when they go camping usually not because they drink contaminated water but because their hygiene goes down the tubes). A study in the northeast found that muskrats had a prevalence of for trophozoites (the stage where the parasites is actually parasitizing, rather than just being transferred from beast to beast) of 96%!!! while for beavers it was less than 15%. There are two muskrats living in the lodge with the beavers and were here well before the beavers established their home and will be here well after (they don't share the same resource depletion strategy as beavers). It seems unreasonable that they'd be testing for Giardia sp., however, and I'm sure there's another reason why the beavers need to go. I'd love to know...

Where: Retention pond under powerlines in Centennial Woods

The amazing capacity of beech to stump sprout. Look at all those latent buds! 

Tuesday, December 18, 2012

Wild hive!!

What: Conner Roberts, a student in my CCV class Natural History of Vermont, found a wild hive of bees in our last class. We weren't sure at first if it was active, but putting my ear up to the hole you could definitely hear a buzz coming from inside!! When I took Zac out to see the hive he knocked and you could hear a furious buzz emanate from the hive.

I wish I could age the honeycomb based on color and texture so we could estimate how long the cavity had been inhabited by bees. Zac and I assumed that it was at least a couple of seasons old as the comb at the bottom (image below to right) was super dark and dense. The comb hanging down (image on left) seems like it's from this most recent season.

Ecological notes: A lot of folks ask me what bees do in the winter. They are such excellent pollinators because they need to collect and store enough nectar to sustain a population of a few thousand during the winter. The nectar is fanned and evaporated down into honey, then capped and store to be eaten during the long winter. The honey fulls their little bodies as they huddle and shiver to maintain the hive at a temperature of around 80 degrees! By staying active, they generate heat (much like running around or doing jumping jacks to stay warm on a cold day.

Pulp at base of pine (about 1/2" thick,
mix of pulp, seeds, and bee carcasses!
Where: Centennial Woods, old (maybe 150 year old) white pine tree that died about 15 years ago in the 1998 Ice Storm. The scar was created much longer ago and there had been enough time for carpenter ants to invade the tree, hollow much of it out, and then abandon their nest. I'll post more on the 1998 ice storm sometime this winter.

Other notes: Zac brought up the idea of search image. This is the second wild hive I've found, and they share quite a few features. Here's what we noticed that might help us cue in to future sites for a wild hive

  • Near an open field (about 20' back from edge)
  • Within 100' of flowing water 
  • In a hollow white pine
  • White pine had several pileated holes in it (both were hollowed out by carpenter ants)
  • Lots of pulp at base of tree
  • Opening to hive elongated vertically, one hive was about 5" tall, this one was closer to 15"

Friday, December 14, 2012

Beavers in the Retention Pond (Part IV)

I'd love to not be posting exclusively on beavers, but they've been on my mind an awful lot these last couple of months. Other stuff is still happening (like a wild hive of honey bees a student of mine found nestled in an old white pine), so more to come on that later.

Other notes: Following up on my Monday post, the second reason that I'm upset by the way the "beaver problem" was handled is that it shows a lack of transparency and input from public voice. It's not surprising that Centennial Woods holds a dear spot in many people's hearts. Every time the University or City proposes some other development in or around CW, it just galvanizes the residents and students that love it. We want to have a say in the shaping and management of CW, to make sure that the emotional connection, and personal experience of the woods holds weight in how the land gets managed and stewarded. The decision (and lack of public input) doesn't appear to take this in to consideration; it doesn't even show a huge consideration for or knowledge of the ecology of that area. Even if Fish & Wildlife said that the beavers could be trapped and not moved, that doesn't mean that that's the other only option. I see two sets of options.

The first in relation to the beavers:
1. Trap all the beavers
2. Relocate the beavers
3. Do nothing
4. Wait until spring to see if beavers leave on their own, and then return to questions 1-3

The second set of options is what to do after the beavers are gone
1. Install beaver baffles around the outflow pipes
2. Cut down trees around pond to remove habitat
3. Do nothing

I'd prefer options 4 and 1. Again, people love this area and want input. Much like CW, few animals are as charismatic as a beaver is. These beavers in particular had become small-time celebrities - so when FWS says "yeah, go ahead and trap them" their comment is on one hand practical and on the otherhand completely ignorant of the context of this specific case - how embedded in the education of many students and hearts of community members these beavers were.

Two of the boys I mentor, one 7 the other 9, came out to Centennial Brook with me last year to meet the parents of one pair of these beavers. When I told the older boy the beavers had moved back in to Centennial Woods, he gathered up a group of his friends and brought them out to meet these beavers. While out visiting the beavers, Sam (the TA for my Natural History of Centennial Woods class) ran into them and they exchanged stories and watched three beavers making last minute preparations for winter, caching beech, cherry, and birch saplings near their lodge. The following day the boy brought his mom and grandma to the pond to meet Melvin and the other two beavers. I got to follow up with them and exchange more stories. Almost every time I go to the pond I meet up with someone down there and we share stories. The beavers have become an anchor for those of us who are connected to Centennial Woods.

It would be amazing if management decisions as sensitive as this were based not on relative ease, but took time and weighed multiple options with multiple voices. It might take more time, but it would empower community members and students to share their voice and make sure that management decisions reflect the needs, desires, and heart of the community that they effect. It'd be great if making "the right decision" included more that just a dialog about how to maintain the functionality of the outflow pipe. How wonderful if the list of consultants contacted for this decision included people deeply connected to the land, who knew this land not from a distance, but hold its stories in their hearts.

Wednesday, December 12, 2012


What: While out at the retention pond in Centennial Woods the other day I spotted a most gruesome scene. Actually, within a little more than a square foot there were three cool finds. See if you can spot them (or at least what I thought was cool) in the photo above.

1. Golf ball. I've seen staff from UVM Grounds on numerous occasions hitting golf balls down into the retention pond. I picked up about a dozen yesterday. Most of them are driving range balls, but occasionally a nicer Titleist ball will show up.

2. Deer scat. A neighbor tipped me off a couple years ago that in the winter, deer in the area often spent their mornings grazing on the north side of the retention pond. That slope has great southern exposure and gets warmer before the other areas - it also has a lot of ground cover. I was surprised, however, to find a few fresh piles of deer scat in the ponded area. I haven't seen their tracks within the fence in the past few years.

3. De-brained short-tailed shrew (Blarina brevicauda). Easily the coolest find was a de-brained short-tailed shrews. Much like grizzlies that eat salmon heads during the salmon runs, in times of plenty members of the weasel family (Mustelidae) will consume only the most delectable parts of their prey. And apparently for weasels that's the brain. According to Mark Elbroch, chipmunks will also eat the brains of mice and leave the rest, which was news to me as I didn't know that chipmunks would eat prey that large.

Shrews are toxic to most mammals (they secrete a venom in their saliva that helps incapacitate larger prey). A mammalogist friend got bit by one a few years back and his arm went numb - imagine the effects on a green frog! I have found two half digested shrews thrown up by red foxes. Here the mink ate it's brains and so didn't have to worry about poisonous saliva. I assumed mink (Mustela vison) and not one of the other smaller weasels (long- and short-tailed weasels) as there were tracks about 15' away in a little stream. Mink also prefer aquatic habitats.

It was a pretty neat find and the second mink kill in that spot in the last couple of weeks.

Where: Centennial Woods

Other notes: Miraculously the fourth beaver (well now the third since UVM killed one of them) showed up again. While out the other night I could see two of them and heard a third making a low grunting noise. All three of them, at about the same time, started making that noise. It reminded me of when my chickens make a really uncomfortable clucking sound when our backyard woodchuck comes around. It's not a sign of imminent danger, but a signal that another presence is in the area - I wondered if the beavers were grunting at the fox that I've seen tracks from in the last week.

Monday, December 10, 2012

Beavers in the retention pond (Part III)

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Beaver clearing trail for a beech sapling

What: Centennial Woods feels a bit emptier today. On Friday afternoon I got the very sad news that UVM was kill trapping the beavers that many of us have come to know so well.

What I know so far is that they have killed one of the three beavers, the one we called Melvin, using conibear traps. There are three conibear traps set up on well-worn trails running between the upper and lower reservoirs of the retention pond. Conibear traps are incredibly effective at killing animals. While they can be baited, these aren't. UVM hasn't locked or closed the gate to the detention pond in over a year and with regularity I find mink, gray fox, raccoon, red fox, deer, domestic dog, and domestic cat tracks in the pond (this morning fresh raccoon and red fox tracks on the wet snow inside the gate). While the traps weren't baited when I checked them, they're located in access points the beavers use with regularity. Trappers place traps where their quarry go. And where their quarry go so do their predators - or anything curious about their scent. This is why Conibear traps also kill so many beagles and other domestic dogs that investigate the one place around a beaver pond where a beaver leaves its scent on the ground (you can find lots of depressing articles on beagles found dead in these types of traps).

Sam and I spooked the beaver while
coming down to check the game cam

Rose Leland told me on Friday that this was the best course of action and that everyone they had talked to recommended this. I find this problematic for two main reasons. I'll post my first here, and the second in a couple of days. First, it's irresponsible management. The beavers had obviously moved in during the summer, immediately backing up the outflow pipe, felling several large beech trees that landed on the fence, and built a visible lodge. All of this is easily visible from UVM's Ground's office and the spot where UVM Grounds employees hit golf balls down into Centennial Woods. They clearly could have seen the effects the beavers were having.

If the beavers were indeed a problem, UVM could have done something at that time to a) beaver-proof the fence around the retention pond, and/or b) transplanted the beavers. The beavers did move out of the pond sometime during the late summer (perhaps UVM did transplant the beavers). But because the habitat and access to it still existed, it would only be reasonable to assume that beavers would return, which they did in late September. Again the signs of their presence was obvious. UVM's negligence in dealing with this until December (almost 10 weeks later), meant that options were severely limited as it's now too late in the season to transplant them. But even the assumption that killing them is the only way to deal with them (if you believe dealing with them is even necessary) is false as beavers have been known to adopt other beavers in their home territory. As I mentioned in an earlier post, the initial pair of beavers adopted the second pair after UVM destroyed their habitat at the other retention pond. An assumption on my part, but due to last year's long growing season and tame winter, beavers this year should be better off and have larger caches. They would, therefore, be more likely to adopt other beavers. Had UVM responded sooner we wouldn't be mourning the loss of a beaver that had touched the lives of so many.

Friday, December 7, 2012

Beavers in the retention pond (part II)

What: I went back and set the game cam up further back from the fence. It doesn't quite capture them crawling under the fence (I put it too far back), but it does give a pretty good sense of how curious and observant they are. They definitely, in both this video and the previous one, noticed the game cam and spent time to investigate it.

Ecological notes: The three or four beavers that live in the pond are two pairs. The second pair moved in about 4 weeks ago when UVM Facilities destroyed the habitat surrounding the other constructed retention pond by the Sheraton. With no food the beavers headed down stream, found this pond and took up residency with them.

I think that two of the beavers were siblings (one from each pair). And I think that they're probably also the same beavers that were living here last spring. Sam and I have both been watching the beavers in the spring, and it took time to earn their trust (where they wouldn't slap their tails at us). I would assume that this beaver remembered me (and the trust it had for me), which is why it only took a couple times to have it come right back up to me.

Where: Retention pond in Centennial Woods.

Wednesday, December 5, 2012

Beavers in the retention pond (Part I)

What: Sam and I went out last Tuesday afternoon (11/27) to set up the game cam. They've got a number of trails that run under the fence around the retention pond that they've used so we decided to stash some aspen on the uphill side of the fence and put the game cam facing the water on the downhill side so we could get video of them dragging the branches back to the water.

We got about 70 videos starting at 4:30pm and ending around 4:30am. The beavers used the path about every 30-45 minutes or so for the whole 12 hours. The video is a compilation of the three beavers making foraging trips from the retention pond to the beech stand (we caught about a dozen trips on camera). The photo to the right is of our second set up to get shots of the beavers crawling under the fence. The game cam is attached to the beech log in the foreground.

Ecological notes: There were 4 beavers in the pond three weeks ago, but we've only seen 3 at a time in the past couple of weeks. Their cache seems to be primarily beech, with some red maple, white ash, elm, white birch, and witch hazel in the mix. They've also been eating heaps of staghorn sumac, scant black cherry saplings, and an occasional glossy buckthorn. Stay tuned, as there are more videos to come (with all the warm weather, the pond should stay thawed for at least another week or so and they'll be out and about)!!

Where: Retention Pond under powerlines in Centennial Woods