Olfactory enrichment for cats: alternatives to catnip

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It is well known that cats, particularly indoor cats, benefit from environmental enrichment as a way of staving off unwanted behaviors such as inappropriate elimination or aggression. One of the common methods for providing this enrichment is with catnip. Interestingly, about a third of domestic cats, as well as most tigers, display no response to catnip at all. In an effort to identify effective alternatives to catnip, a study in BMC Veterinary Research evaluated the feline response to 3 other plant materials: silver vine, Tatarian honeysuckle, and valerian root.¹

Study design

The researchers recruited 100 randomly selected cats for the study. All cats were over 6 months of age, and most (n = 82) were housed at a shelter or cat sanctuary. Cats with upper respiratory tract infections were excluded. Exact adult age was available for only 89 cats, and these cats were divided into 2 groups—those 4 years, 10 months of age and younger and those older than 4 years, 10 months—to determine the impact of age on responsiveness. Cats were also classified into 3 behavioral categories: those that hid and avoided human contact, those that showed interest in humans and enjoyed being petted when approached, and those that immediately approached humans and wanted to be petted.

Four plant materials were used in the study: dried, cut, and sifted organic catnip (Nepeta cataria) leaves and flowers; dried, cut, and sifted valerian (Valeriana officinalis) root; Tatarian honeysuckle (Lonicera tatarica) wood and sawdust; and powder from dried silver vine (Actinidia polygama) fruit galls as well as normal dried silver vine fruit. Fruit galls are fruits that have been invaded by insects, in this case, the midge Pseudasphondylia matatabi.

Cats were exposed to the plant products by placing the product inside a thin, porous sock or by spreading it onto a 0.5-square-meter piece of frieze carpet that allowed exposure to the plant material while preventing ingestion. The amounts and volumes of the catnip, valerian root, and Tatarian honeysuckle were chosen to ensure maximum exposure to active compounds that would allow for a positive response (Table 1). Due to the high cost and limited availability, the amount of silver vine used was based on the manufacturer’s recommendation and had been previously demonstrated to be sufficient to elicit a response.

Table 1. Amounts and placement of plant materials studied

* Tatarian honeysuckle was also offered as a 10-cm piece of wood.

The socks and carpet squares were made easily accessible to all cats but were not forced on the cats or repositioned when the cat walked away from the item. An identical carpet square with no plant material and an empty sock were also made available to the cats to act as negative controls.

All cats were exposed to all plant materials, at separate times and in random order, for up to 1 hour on at least 2 different days. The majority of the cats were also exposed to the Tatarian honeysuckle wood. A washout period of at least 5 minutes between plants was used to avoid any carryover effect. When a positive response was noted, the plant material was removed to prevent response saturation and offered last on subsequent days.

Positive responses included licking, sniffing, shaking the head, drooling, rubbing the chin/neck on the sock or carpet, raking, or rolling over. A negative response was recorded if the cat did not react at all after 2 exposures to the plant material.

A separate group of 9 randomly selected cats was used to determine responsiveness to various parts of the silver vine plant. These cats were exposed to 20 g of dried silver vine fruit galls; 20 g dried normal silver vine fruit; 1.5 g powder of dried normal silver vine fruit; sun-dried and fresh leaves of dried normal silver vine fruit (2 and 5 g, respectively); and 15 g woodchips made from commercially available silver vine wood sticks. All plant materials were presented randomly to the cats within a sock and removed after the cat stopped engaging with the sock for at least 1 minute or after 5 minutes of indifference.

To evaluate response in big cats, the study authors enrolled 9 tigers and 5 bobcats living in an exotic cat sanctuary. The tigers were presented with catnip (20 g) or silver vine powder (1.5 g) uncontained or within a folded paper bag with small holes cut in the side. The bobcats were offered plant material presented in a crumpled-up paper bag with no holes in it. For each presentation, the plant material was placed within 0.5 m of the cat’s face and each cat had a minimum of 5 minutes of exposure to each material.

All plant materials used during the study were then subjected to gas chromatography and mass spectrometry to determine the levels of olfactory compounds previously known or suspected of stimulating cats.

Study findings

The researchers found that 79% of domestic cats responded positively to the silver vine whereas 68% responded to catnip, 53% to Tatarian honeysuckle, and 47% to valerian root. Males and females appeared to be equally responsive. There was no difference in responsiveness based on age, but the researchers did note a lower response intensity in older versus younger cats, specifically for catnip. They also noted that shy or scared cats were just as likely to respond as affectionate and friendly cats.

Of note, 31% of cats did not respond at all to catnip; however, 71% (22/31) of these cats did respond to silver vine, 32% (10/310) to Tatarian honeysuckle, and 19% (6/31) to valerian root, suggesting that these are effective alternatives to catnip. Further, among the 21% of cats that responded to only 1 plant material, that material was most often silver vine.

Among the 9 cats exposed to various parts of the silver vine plant, the researchers found that the most response was elicited from exposure to dried silver vine fruit galls as opposed to leaves, wood, or normal silver vine fruit.

In the big cat group, tigers showed little interest in either the catnip or the silver vine, and 5 of the 9 tigers actually backed off and walked away from the silver vine. In contrast, 4 of the 5 bobcats responded positively to the silver vine and only 1 to the catnip.

Upon chemical analysis, cis-trans-nepetalactone was found in highest concentrations in catnip and considered to be the compound to which cats responsive to catnip react. Among the various forms of silver vine tested, actinidine was found in highest concentration in the dried fruit galls. The levels of other compounds, including iridomyrmecin and isodihydronepetalactone, were higher in silver vine than in either Tatarian honeysuckle or valerian root, and may also contribute to the olfactory response in cats.

Future studies and potential limitations

The authors acknowledge that other undetected compounds may also play a role in responsiveness and that well-controlled studies using isolated, pure compounds are needed. They also note that while silver vine is widely believed to be safe and nonaddictive, scientific data are lacking.

Although it is not clear why the silver vine fruit galls elicited the greatest response when compared with other parts of the plant, the authors postulate that volatile compounds secreted to repel the midges may act as an olfactory stimulant to cats.

Implications for clinical practice

This study provides evidence that, for cats that do not respond to catnip, silver vine, valerian root, or Tatarian honeysuckle may provide a safe and effective alternative. Although further studies are warranted, these plant materials may also be of benefit for training or socializing cats in shelter situations or, given the lack of evidence for efficacy of synthetic feline pheromones, to alleviate stress in cats during transportation, boarding, or medical procedures.

Jennifer Garcia, DVM, DACVIM, is a small animal veterinary internist and medical writer based in Texas.

Reference

1. Bol S, Caspers J, Buckingham L, Anderson-Shelton GD, et al. Responsiveness of cats (Felidae) to silver vine (Actinidia polygama), Tatarian honeysuckle (Lonicera tatarica), valerian (Valeriana officinalis) and catnip (Nepeta cataria). BMC Vet Res. 2017;13(1):70. doi:10.1186/s12917-017-0987-6