The swift fox (Vulpex velox), native to North America, was declared extinct in the state of Montana (USA) in 1969. In response, various entities reached an agreement to begin a reintroduction. program to build a fox population on the Blackfoot Indian Reservation, northern Montana. Thirty years after their extinction, the first humans were released and the reserve once again saw strong wolves running across its plains. This program was not only able to successfully recover this species but was also marked before and after for conservation because it considered for the first time the personality of the animals released.
Now, there is no doubt that animals, whether fish or invertebrates such as crustaceans, also have personality, which is defined by the differences in the behavior of individuals of the same species. These differences should be consistent over time and across different situations or contexts. In the same way that there are people who are more social than others, more aggressive or braver, some animals also show these differences. Currently, the study of animal personality is one of the fastest-growing fields in biology and has very interesting applications; one of them is in the field of conservation and, in particular, in the restoration of species.
Every reintroduction program worth its salt includes a thorough evaluation of the process. If this does not happen, we will talk about releasing the animals or something, but not about reintroduction. The programs conduct studies to ensure that the animals meet the appropriate health and behavioral criteria to survive in the wild, such as getting their food or fleeing from predators. In addition, after the release, the animals are monitored for months or years and the reintroduction is only considered a success if they breed and can create a stable and long-term population.
The scientists in charge of the reintroduction of the swift fox want to go further and also study whether the personality of the foxes affects their survival in the wild. In particular, they decided to focus on one characteristic: courage. The wolves are from a captive colony, where personality tests can be done. To do this, they introduced a new object inside the animals and measured the time it took each to approach it.
Those wolves that repeatedly are more likely to explore new stimuli are considered braver. Therefore, they examined 31 people within two months of release. The results were enormous: the bravest died before the cautious.
According to the authors of this research, captive wolves may be less fearful than wild wolf would be. Stress affects reproduction, therefore, those individuals who are less stressed in captivity because they are less afraid will reproduce more. After many generations, it is expected that new generations of these wolves will be less afraid of new stimuli. Therefore, when returning to their natural habitat, they explore the territory more and avoid cars less, which makes it easier for them to die from collisions. At least, this was the case of the only two deaths whose cause could be determined. Thanks to this research, the importance of considering the personality of animals in conservation efforts is recognized.
Since then, other reintroduction programs have included personality studies. In particular, aspects such as courage, bravery, and sociability are considered. For example, to reintroduce social species, we aim to have a wide variety of personalities among individuals, as this facilitates coexistence. This is what is suggested by the hypothesis of social niche specialization, where many studies prove it in species such as shrews, spiders, and fish.
Now, if a clear conclusion can be drawn from all these studies, it is that there is a great variability in the results. Even within the same species, the optimal personality to survive may differ depending on the environment and time. Bolder people are more likely to take risks and may die sooner, but they also reproduce and occupy new territories faster. Each character has advantages and disadvantages, and the balance can easily tip one way or the other depending on the circumstances.
The ‘game’ to survive
A clear example is the European mink reintroduction program in Estonia, which evaluates the survival capacity of these animals based on their propensity to explore new territories. Surprisingly, at first, the less exploratory individuals were more successful, but within a year the tables turned. This may be due to external factors, such as variation in prey abundance, or because the second year is drier and warmer. The important thing is that the population remains stable over time thanks to the fact that the personality of the minks is diverse.
Some authors have suggested that animal personality differences can be explained by the so-called game theory. Suppose that the population of animals in which the most aggressive individuals win will fight against the most docile animals and multiply. In this case, being aggressive is an advantage and, over time, the population will be dominated by this type of individuals. There comes a point when the fights are so frequent and deadly that the tables can be turned. Those animals that are more shy and peaceful participate in fewer conflicts and are more likely to survive. In this way, evolution favors certain personality traits or others in nature and diversity is maintained over time.
The relationship between an animal’s personality and its ability to survive is extremely complex and this field of study has great potential. Every reintroduction program must find the ideal personality types to survive in the wild for as long as possible. At a time when species are going extinct faster and faster, any small push toward conservation is necessary.