There are subtle changes prior to earthquakes that many animals can perceive. It is true that there are also stories about snakes leaving their burrows, dogs that bark excessively, or birds that fly days or even weeks before they occur. In these cases it is more debatable that these behaviors occur. But the truth is that many animals are capable of detecting earthquakes, moments before they occur.
When an earthquake occurs, vibrations run through the ground at a level that we cannot consciously perceive. However, this type of vibrations, the primary ones, travel at twice the speed of the secondary ones, which cause all the damage. Some animals, which they are capable of, is to detect the primary vibrations before the secondary ones arrive. This interval of time, of at least two minutes, gives them the possibility to react before the loud noise arrives.
Scientific evidence
A study from the Open University in the UK found evidence. The tensions that build up throughout the Earthquake fault lines release electrically charged particles. These are transmitted by rocks, producing chemical changes in the groundwater. In this case, yes It could be understood that the toads suddenly left their ponds days before. A good example of this would be the earthquake in L'Aquila in 2009, Italy. The pond where the toads were found was located 74km from the epicenter of the earthquake. The earthquake was 6,3 on the Richter scale, and caused great damage, among many houses completely destroyed.
Other assumptions that could be attributed by analogy to what has been described, are the behaviors of birds and bats. It is possible that positive charges influence the electromagnetic fields that bats and birds use to orient themselves. But there is no direct link that has been substantiated yet. So for now, the most plausible remains the primary vibrations that many animals can perceive. That is the scientific reason why they can react before the strong earthquake hits.