Friday, February 1, 2013

Raising Tadpoles: Red Legged Frogs in South Western BC

Young viable Red Legged Frog spawn.
NOTE: BEFORE READING THIS, read my more recent post on the issue:  Raising Tadpoles: I was wrong.

Older Red Legged frog eggs: note the tails on the developing tadpoles.
Every spring people ask me how to gather frog eggs from a pond, raise them inside, and release them again, because they know we've done it in the past. So here is finally a public answer that I can just direct people to! Raising frogs is not only fun but also hugely rewarding and, in my opinion, a very good ecology lesson, since it's crucial for the frogs' survival that you observe and replicate their natural environment.

The big jelly clumps of frog eggs that are found in ponds around Bowen right now are the eggs of red-legged frogs, which are blue-listed, meaning that they are a species at risk, primarily through habitat loss, pollution, and the introduction of invasive species. It is very important, if you are raising frogs, to raise local frogs (as opposed to other species available for purchase), and to release them back to where the eggs were found, once they develop hind legs. Raising non-local species can
developing spawn in the aquarium
mean the introduction of invasive species, causing further decline of the indigenous species and tipping the balance of the whole ecosystem.

*If you find stiffer clumps of eggs, more oval-shaped and dense, and often deeper in the water, around sticks or especially lily stems, these are likely eggs of Northwestern Salamander, and are much more difficult to rear successfully. I don't recommend it, and this article is about raising the Red Legged Frogs.

Hatching day!
Of course, physically removing the tadpoles from their pond is not the only way to learn about frogs. Please also consider monitoring and
observing on site and reporting directly to frogwatch... the program is a joint work between Environment Canada's Ecological Monitoring and Assessment Network and the Canadian Nature Federation.

Here is how to raise the red-legged frogs:

Getting bigger! At this stage some of their internal organs are visible.
  • Start looking at your local still-water pond in early March. Eventually you'll discover frog eggs, if there are any to find, and as you watch them, you'll see that the viable clusters have tiny black dots in the centres. If they're grey or white they may have died; so pick another cluster! If you're a little later, you'll find that the black dots have become clearly definable little black tadpoles, curled up and flicking back and forth in their tiny eggs.
  • Before actually taking the eggs, study the area where you find them, and try to replicate that environment.
  • Frogs lay their eggs in very still water, among plants that will protect and feed the tadpoles, when they hatch.
  • Make sure they have a large enough aquarium with STILL water -- no filter or bubbler, as this will disturb the water & particulate. Usually at least a 20 gallon tank is necessary. Larger is better!
  • Scoop up some of the plants, sticks, and dirt from wherever you collect the frog eggs, and carefully add it to the aquarium.
  • When you put the eggs in the tank, do it carefully, so that they don't fall apart. Try to keep them attached to whatever they were laid on (stick or reed, etc).
Water changing isn't a chore because there's so much to discover.
  • You'll need to go back to the water they were laid in to bring fresh water for them, on a regular basis. Partly, this is to make sure the water continues to have enough oxygen for them; partly it's to lower the nitrogen levels (from their poop) and to replace with cleaner water.
  • Bring the water in the house to where you keep your tank, and let it warm up for a few hours to a day, until it's about the same temperature as the tank.
  • Carefully scoop out about 1/2 the tank (more, when they're big tadpoles) one cup at a time, and replace it by slowly pouring one cup at a time into the tank, to refill.
  • Take care not to introduce any big dragonfly larvae or leeches; they'll eat the tadpoles! Or, if you do, (because it's interesting!) take them out before they decimate your stock entirely too much!
  • EGGS: Change water every week or so.
  • TADPOLES: the more they grow, the more often you'll need to change as they eat and poop more. In the end you'll probably have to do some every day, especially if you have a lot of tadpoles.
  • Let some go early!! As they grow it will become more and more difficult to keep up with feeding and water changing, and the healthiest thing to do is to let a few go every week, so that those remaining have more space to thrive. And it's possible that those released earlier have more time to adapt to the wild and live healthier lives in the long run.
Yum... decomposing lettuce.
  • The baby tadpoles will begin by hanging on and eating their eggs. They're very fragile at this stage, and so are the remaining eggs. Be VERY careful not to disturb them when replacing water. Maybe a good idea to replace less water more often at this stage.
  • Tadpoles eat decomposing plant matter. Find a few different types of pond weeds (they only eat some), especially those with round leaves, and also a boiled lettuce leaf. Watch carefully which types they eat, and find more of those. When they're bigger, you'll be boiling bits of lettuce nearly every day for them, but try not to give them too much at once, or it will make the tank too filthy, and they can suffocate.
  • At first they'll hang on things by sucking on with their mouths, but once they develop legs they like to use them, so make sure there are some sticks properly wedged in (not just floating), so that they can climb around on them.
  • Once they get forelegs they begin to come out of the water, and will need a branch that sticks out.
  • Once their tails begin to shrink, they'll start jumping, and that's time to let them go, before they jump out of the tank and die in the house. Don't wait too long after they begin to develop forelegs; the jumping happens faster than you think!
  • Take them to where you originally found them, and slowly (every few minutes) add cups of the water to their container, until they are accustomed to the new temperature. Don't rush it! This should take a loooong time. If you can, it's even better to slowly acclimatize them by moving their tank to a cooler location every day (but never in the sun!) until it's outside on the last day, at which point you go to the pond and start adding cups of water as above.
  • Bid your friends farewell, and wish them a happy life!
  • Be careful not to drive over them when they migrate across the road, later in the year!
The following are the most common problems I've seen, which generally mean the tadpoles die and the whole project fails. Avoid them!
  • The aquarium is too small for the amount of eggs or tadpoles. I would estimate that you don't want the clump of eggs to take up more than about 1/10th of the volume of the tank. The real reason this is a problem is because you cannot safely exchange enough of the water, often enough, to keep them well-supplied with oxygen and clean water.
  • The aquarium is in the sun or near some heat source, and the water gets too warm.
  • The water gets contaminated by kids' enthusiastic activities!
  • Leeches, dragonfly larvae or other predators are introduced with the setup or exchanges, and they devour the tadpoles! Mind you, this is interesting to observe, and definitely helps recreate the real-life scenario they'd be living with in the wild!

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