Murine genomes share great similarity with the human genome, which has made both mice and rats fantastic models for a wide range human disease research. Rats are the second most used laboratory animals after mice. To the uninitiated, rats appear to be larger versions of mice, but they are actually two different species.

Mice evolved from Mus musculus, which are widely distributed all over the world. After long-term artificial breeding and selective breeding, more than 1,000 inbred strains and independent outbred stocks have been bred for research use. Rats, also known as Norway rats, belong to the class Mammalia, the order Rodentia, and the Muridae family. Laboratory rats are a selective breeding variant of Rattus norvegicus. As commonly used laboratory animals, rats and mice are widely used models in various fields of biomedical research.

In previous Technical Bulletins, we have shared information about mouse behavior. Presumably, everyone has a basic understanding of their behavior, response and the influencing factors behind it. So, how much do you know about rat behavior?

1. Docility & Handling

Mice are smaller in size and more docile in temperament, so they are easier to grasp and immobilize; Rats are relatively large in size, and their global muscle strength is relatively strong. When grasping and immobilizing a rat, the required strength and difficulty of operation are greater than for a mouse. However, frequent and gentle handling can increase the docility of the rat, which can reduce the possibility of injury to the operator and reduce the stress of the rat. Infrequent or rough handling can induce fear in rats and is often used as a stressor in research projects. In rat behavioral studies, adaptive feeding domestication of rats in the pre-weaning and weaning periods affects the degree of stress induced by subsequent manipulations and alters rat responses. "Fun-filled" manipulations can reduce stress in rats when performing manipulations such as injections.

2. Sound

Operational handling can cause the rat to emit >22 kHz calls, referred to the typical rat alarm calls. In a cage, stress-induced vocalizations by one rat can affect the behavior of other rats within hearing range, making manipulation of other rats more difficult. Another interesting fact about rat vocalization which illustrates its importance in rat behavior, is that rat pups vocalize in the ultrasonic range even before their ears are developed enough to hear, probably to signal their mother.

3. Circadian Rhythm and Diet

Rats are most active at night, but will also move and eat during the day. In addition to this, they are more active in the morning than in the afternoon, and this circadian rhythm affects behavioral tests. For example, the pain threshold is often assessed by the tail-flick test, whereas the tail-flick latency of female rats is relatively short in the mid-dark cycle, estrus, and post-estrus.

4. Solitary or group-living

Rats can be kept individually or in groups. In general, male rats are less aggressive than male mice when housed in groups, and they also do well when housed individually, which is the norm in many toxicology and safety assessment studies. Although historical experience shows that laboratory rats appear to adapt well to individual housing, there are marked physiological and behavioral differences in rats housed individually compared to rats housed in groups. It is strongly recommended that, where possible, social animals such as rats be housed in socially compatible groups.

5. Environmental Materials and Enrichment Programs

When given a choice, rats showed a preference for the solid floor, bedding litter, and nesting material consisting of large grains of poplar wood chips. Rats chewed inanimate objects such as wooden blocks, nylon bones, and balls when presented with items as part of an environmental enrichment program. The provision of environmental enrichment items is an important part of the husbandry management of high-quality research animals, but as in the case of group housing, it can significantly alter the baseline behavior and experimental responses of rats. Therefore, it is necessary to evaluate the environmental enrichment items provided to rats for potential experimental impacts.

Cyagen's Neurobehavioral Platform

Animal behavioral tests are important tools used in neuroscience research to evaluate behavioral phenotypes and establish rodent models of neuropsychiatric indications. Researchers are able to explore complex phenomena of life through a variety of behavioral assessments, including: the comprehensive evaluation of animal models' learning and memory, psychology, motor coordination, social behavior, and other phenotypic aspects of neurological disorders.

Rats and mice are the most commonly used animal models in neurobehavioral research due to their high degree of genetic homology with humans and wide variety of established disease models. After years of preparation, Cyagen's senior expert team has developed a rat and mouse neurobehavioral assessment platform. Cyagen offers rat and mouse behavioral assessment services using professional recording and analysis systems, including: water maze, novel object recognition test (NORT), Y maze, rotarod, open field test (OFT), forced swimming test (FST), elevated plus maze (EPM), and other types of rodent behavioral assessments. You can choose to use our behavioral platform to accelerate the phenotype evaluation process and conduct experiments on your own, or you can entrust Cyagen to provide one-stop services for your research model project. Our comprehensive services cover the entire process of model generation, from transgenic/gene targeting strategy design, model development, breeding, behavioral testing, phenotype assessments, evaluating surgery/drug treatment, and pathological marker detection; we have cultivated these capabilities to help you complete your research goals in a shorter time. Request a free consultation by contacting us at 800-921-8930, or email