Different types of enrichment can be useful for different types of behaviour. Enrichment is, in most cases, classified by the effective stimulation of these behaviours. Many enrichment items are not limited to one type of enrichment. However, what are the different types of enrichment?
Sensory enrichment focuses on the stimulation of the animals' senses. You can divide it into four subcategories: visual enrichment, olfactory (smell & taste) enrichment, auditory (sound) enrichment, and tactile (touch) enrichment. These senses are all important means of communication and are routes of gathering information about its surrounding environment. As an essential form of enrichment, care needs to be taken when providing sensory enrichment. You are not always aware of what information you are communicating towards your animals. Most types of sensory enrichment are a passive form of enrichment.
Food-Based / Food-related
Food-based enrichment can be defined as "the manipulation of food or method of providing food". This type of enrichment focuses on the food presentation to make feeding more challenging for the animal. A variety of feeding methods and food presentation encourage animals to work for their food. It can also be enriching providing a novel food item. The ultimate goal is to stimulate and extend the appetitive and consummatory behaviours of an animal. Often zookeepers provide puzzle feeders, which is discussed in cognitive enrichment.
Environmental / Physical Habitat / Structural
Structural enrichment, also called 'physical habitat enrichment', is defined as "alteration of the physical elements of the enclosure". Its main goal is to stimulate exploratory behaviours and collecting information. This enrichment is mainly provided to prevent boredom and keeps the animal physically healthy by encouraging it to become more active. This kind of enrichment, which is different from tactile enrichment, is ranked as important but is not often provided. The physical environment should be frequently altered and switched so animals do not become too familiar with their environment, which causes boredom and can eventually cause stereotyped behaviours.
Manipulative / Cognitive / Tactile
Almost seen in every zoo, this type of enrichment is described as "cognitive and mental stimulation that requires problem-solving of different levels of complexity". Zookeepers spend a lot of time developing the most creative enrichment ideas, to keep animals mentally engaged. It focuses mainly on the mental health of animals. Most used devices are puzzle feeders, where animals are cognitively challenged to be rewarded with food. With different objects, animals are stimulated for investigation and exploratory behaviours. Animals with a higher form of intelligence need to be more mentally stimulated to excite their cognitive abilities.
This form of enrichment is focussed on organized interactions between conspecifics, interspecific or human-animal. Sometimes it is also possible to use a substitute as social enrichment (i.e. plush toy). A well-known and most common form of social enrichment is animal training. Training can be very beneficial for animal welfare by providing cognitive stimulation, increasing social play, decreasing inactivity, and mitigating social aggression during feeding.