If you’re a pond owner or enjoy being in nature, you’ve probably stumbled upon frog spawn at some point. The egg accumulations of amphibians can be recognized immediately by the enclosing egg jelly, which, depending on the species, holds between 50 and 10,000 eggs, from which numerous tadpoles can develop. Here you can learn how development, rearing and resettlement work.
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recognize frog spawn
If you own a pond or are often out in the woods and discover ponds with spawn, it is important to know whether these are frog eggs. All native amphibians, including real frogs (Rana), toads (Bufonidae), tailed amphibians (Caudata) or toads (Bombinatoridae) continue to reproduce via spawn. The only exception are the salamanders (Salamandra), which give birth to their offspring alive. Because amphibian spawning times overlap a lot, it’s important to know what frog spawn looks like to be on the safe side. You can recognize the spawn of the hopping fellows by the following characteristics:
- Egg size dependent on species
- Spawn is in transparent jelly
- Spawn clump size is determined by species
- can rise to the water surface
- mostly on the ground
- more rarely clumps are attached to plants
The color is also important here. The color of the eggs depends on the spawning season. Eggs from early-spawning species are noticeably darker than those from late-spawning, which is not the case in toads or other amphibians. The spawn of the common frog (Rana temporaria) will be darker than that of the water frog (Pelophylax lessonae), whose mating season extends into July. Above all, however, it is the spawning clumps that indicate frogs. Above all, the flatbreads of the common frog (Rana temporaria) should be mentioned here, which are clearly floating on the water surface.
The spawn is only the first stage of development from egg to finished frog. The development that frog spawn goes through to adulthood is truly interesting and provides a fascinating insight into the lives of the hoppers. The following points influence the development:
- food supply
- water quality
Despite the different spawning times of the individual taxa, the metamorphosis of native frogs from egg to adult takes place in a similar way. Temperatures of 20°C and suitable water in which the spawning is undisturbed are ideal. Frogs usually never lay their eggs when there are fish around. If a good place is found, the development proceeds as follows:
- After fertilization of the spawn, the tadpoles hatch after five to 14 days. The tadpoles move very quickly in the egg and thereby break open the shell. At this point, they only have a rudder tail. They also have gills and a mouth with teeth.
- The tadpoles stay at this stage for anywhere from six to eight weeks. During this time they swim around, grow and eat. Food at this point is algae, plant debris, suspended particles and, after a certain age, even other tadpoles and spawn.
- After six to eight weeks, the rear extremities are increasingly developing. After that, the tadpoles swim with two legs and the rudder tail for some time. The front legs are still hidden until then.
- Another 14 to 21 days later, the actual metamorphosis into the actual frog follows. The front legs develop completely and the so-called “rasp mouth” is no longer used. The tail forms back, as this is the only source of food for the animals, since they first have to develop their actual mouth.
- Now the animals are finally going ashore. If the tail is no longer visible, the mouth is fully developed. The corresponding frog species can already be identified.
Once the frog has landed, it can take up to three years for the animal itself to become sexually mature. Then the frog spawn cycle starts all over again.
The rearing of frog spawn is a complicated issue, as the animals are under strict nature protection in Germany. This means that you must not disturb, destroy or collect the adult animals, their offspring and spawn. Even the rearing of frog spawn itself is not allowed. If you were caught doing so, you face fines of 5,000 to 65,000 euros, depending on the state. Rearing is therefore only possible if one of the two situations is present:
- approval is available
- emergency rearing
A permit for frog spawn rearing is not granted in the majority of cases. Even teachers in schools are not allowed to simply remove the spawn and present it to a school class. This must be registered and approved in advance. If you live in Switzerland and teach there, this project is much easier to manage than in Germany or Austria. Private individuals never have a chance of obtaining permission to breed frog spawn, even if it is in their own garden pond . It is only possible to raise spawn when there is an emergency. For example, if your child brings eggs home after playing, it can be reared to ensure the survival of the eggs. For this you need the appropriate materials and utensils.
When an emergency rearing needs to take place, having the appropriate materials and supplies is paramount. Amphibians are extremely delicate animals and can only grow from spawn to juvenile without disease if a suitable environment is created for them. For that, take a look at the following list:
- 1 x jar
- in fear
- big Stone
- Goldfish dry food
When choosing the vessel, you must pay particular attention to the size and the material. Do not use dark vessels, as these usually heat up far too quickly in the desired location, which can be dangerous for the tadpoles. Likewise, you should never place the spawn in a pond that already has fish in it. These would simply eat up the frog spawn. A transparent container would be ideal, as sufficient sun can still get through it without immediately becoming too hot. Examples of good vessels are:
- Plastic bucket
- water barrel
Make sure the jar holds at least 10 liters, which is enough for about 50 tadpoles. Using this value, five eggs per liter of water, you can calculate exactly how big the vessel needs to be. It also must not be too deep. A shallow water level is recommended. A good size is 30 centimeters long so the tadpoles can swim and 20 centimeters deep so that they have enough oxygen. You can do without substrate for frog spawn, as this would only cause more dirt, which makes the weekly water change more difficult. Stones and the cork bark are indispensable for this.
Frogspawn can be raised in the following way:
- Begin by rinsing the jar with water. Do not use detergents as even the smallest amounts can kill the tadpoles.
- After washing the jar, place the cork bark and stones in the jar. You don’t have to fix the cork bark because it will end up floating on the water. The two materials help the young frogs stay afloat and recharge their batteries during their development. The more spawn you put in the jar, the more resting opportunities should be created.
- Once you’ve prepared the tank, place the spawn in the water. Depending on the species of frog, it will either swim or sink. Place the tank in a location that is very sunny but not in direct sun for hours. The midday sun in particular should be avoided. Sunny locations are important for the good development of the tadpoles, since without sufficient vitamin D they can suffer from deformities such as matchstick legs. The maximum temperature from the sun is 35°C.
- Now wait until the tadpoles reach a length of one centimeter before you give the first flakes of goldfish food. When feeding, you may only give as much as the young amphibians can consume. So keep an eye on them to see if they are being fed too much or too little.
- During the entire time, a water change must take place on a weekly basis. The more specimens you have in the water, the more important this one is. When changing the water, clean the floor with the vacuum and then refill with stale water. If the population is very large, you should even clean daily.
- Watch the animals closely. Once the animals’ front legs have formed, you need to start considering relocation. You can see the front legs quite well. From this point on, the young frogs also begin to use the stones and the floating cork bark as an opportunity to rest outside the water. However, the resettlement still has to succeed as long as the animals have tails. Orientate yourself on the development of the spawn described above. This allows you to estimate how quickly the tadpoles are developing.
Once the rescued frogspawn have turned into young hoppers that are four, you can begin translocation. This is necessary because the frogs can be resettled outdoors without any problems from this point on. The location chosen for resettlement is particularly important here. If possible, the body of water from which the frog spawn came should be used. Likewise, you can choose a body of water that can be found close to the original one if you’re not entirely sure where the spawn came from. This is often the case when children collect frog spawn. The body of water must have the following properties:
- no fish
- vegetation present
- not contaminated
- enough sun available
Carefully quarter the tadpoles in a bucket filled with enough water and some rocks, roots, and bark. Then transport the little frogs to the water and put them in their new homes. After relocating, you must leave the animals completely alone, as they need a few weeks to get used to the location. Stress from human influence can greatly delay the onset of sexual maturity, which is undesirable.