Water intake and consumption behavior of colony and privately-owned healthy domestic cats fed 100% dry, 50% dry and 50% wet, and 100% wet diets: a comparison of research and home environments

Abstract

Dietary moisture is a key determinant of hydration in domestic cats. Yet the effects of feeding isoenergetic diets with varying moisture content on free and total water intake (FWI; TWI), drinking behavior, and the translation of findings from a controlled colony to home environments remain poorly characterized. The objective of this study was to evaluate how dietary moisture influences total and FWI and postprandial vs. fasted drinking behavior in cats fed isoenergetic extruded and canned diets, and to assess whether hydration outcomes observed in colony-housed cats are consistent with those measured in privately owned cats living in home environments. Twelve colony-housed male cats and ten privately owned mixed sex cats sequentially fed three diets for 2 wk each: 1) 100% dry, 2) 50% dry and 50% wet, and 3) 100% wet. Water intake volume, drinking duration, and event frequency were continuously recorded using Felaqua Connect water fountains. Data were analyzed using repeated-measures mixed linear models with treatment as the fixed effect and individual cat as the random effect across days. Drinking behavior relative to meal timing was also evaluated using a repeated-measures approach. A second linear mixed-effects model was fitted, with treatment, environment (colony vs. privately owned), and their interaction as fixed effects and individual cats included as a random effect. Estimated marginal means and Tukey-adjusted contrasts were computed for all treatment × environment comparisons. Daily FWI was greatest on the dry diet, whereas TWI was greatest on the wet diet for both groups of cats (P < 0.001). Across all treatments, cats had a higher FWI during the postprandial period than during the fasted period (P < 0.001). Privately owned cats consumed greater FWI and TWI than colony-housed cats across all dietary treatments (P < 0.001). However, strong positive correlations in daily FWI (r ≥ 0.87; P < 0.001) and TWI between environments (r ≥ 0.79; P < 0.001) indicated a similar response to changes in dietary moisture across environments. Transient increases in water intake were observed for approximately 24 h following dietary transitions. This study compares cat drinking behaviors in colony and home settings and provides novel evidence that cats consistently consume more water in the postprandial period, regardless of dietary moisture content.

The amount of moisture provided in a cat’s diet will impact their daily total water intake and free water intake. Regardless of dietary moisture content, cats typically consume most of their daily free water after a meal.

Introduction

Ensuring cats consume sufficient water to maintain hydration is a common concern for veterinarians and owners alike. Domestic cats are estimated to have a reduced thirst drive linked to their evolutionary origins as desert-adapted carnivores (Pachel and Neilson 2010). Wild and feral cats consume prey that is approximately 65–85% moisture (Plantinga et al. 2011), which historically supplied sufficient dietary moisture, thus they have a lower reliance on free drinking water. Therefore, modern low-moisture diets often fed to domestic cats may challenge physiological mechanisms that evolved under high-moisture feeding regimes. Reports of high variability in water intake (Kosmal et al. 2026) suggest that many cats may not meet recommended water intake volumes and that existing guidelines lack a strong empirical foundation, particularly when diet composition varies among individuals.

The National Research Council (NRC) suggests a total water intake (TWI) of 50–60mL/kg body weight (BW)/d for dogs and cats (approximately 200 to 360 mL for a 4 to 6 kg cat) (National Research Council 2006), based on fluid therapy guidelines, assuming a urinary output of 1 mL/kg/h and insensible losses of 1 mL/kg/h (Schaer 1989). However, these values do not account for differences in species, diet composition or format, activity level, or environmental factors. Previous work on water consumption of cats reports that increasing dietary moisture led to an increased TWI, despite reduced free water intake (FWI) (Carciofi et al. 2005; Wagner et al. 2006; Thomas et al. 2017), as well as increasing sodium and protein content (Hawthorne and Markwell 2004; Zanghi et al. 2018a, 2018b) or dry matter intake have been associated with increased FWI (Carciofi et al. 2005). Reported TWI values range from 145 to 293 mL/day on diets with ∼75% moisture and 103–109 mL/day on diets containing ∼5% moisture (Buckley et al. 2011; Thomas et al. 2017), yet many of these values still fall below the NRC recommendations. Despite these observations, relatively little research has examined how diet-driven differences in moisture content contribute to drinking patterns in the domestic cat, particularly under varying at-home conditions.

Beyond water volume, feline drinking behavior remains poorly characterized. Cats are crepuscular, with peaks in feeding and activity at dawn and dusk (Parker et al. 2019, 2022). One previous study reported a shift toward greater nighttime physical activity, but similar total activity levels in cats fed wet (82% moisture) diets compared with those fed dry (3% moisture) diets (Thomas et al. 2017). However, rhythmic drinking patterns have not been well established. Physiological constraints may also influence drinking behavior; for example, stomach capacity is estimated at 300–350 mL in cats (Halfacree 2014), and meal volume may temporarily inhibit drinking due to gastric distension and neuroendocrine signaling from a full stomach (Wyrwicka 1978). Conversely, consumption of high-moisture diets may reduce immediate thirst while promoting water intake at other times of day.

Therefore, we conducted two studies following the same experimental design, one using a controlled cat colony and the other using privately owned cats. The objectives were to examine how dietary moisture content influences water intake and drinking behavior of cats by 1) assessing TWI, FWI, postprandial vs. fasted drinking patterns, and drinking bout characteristics in facility housed colony cats fed isoenergetic quantities of diets containing 10%, 63%, and 80% moisture under controlled conditions, and 2) comparing the findings between colony cats and privately owned cats living in dynamic home environments to determine if findings from the controlled facility housing can translate to a real-world population and setting where temperature, humidity, enrichment, human activity, and feeding routines vary naturally. We hypothesize that higher-moisture diets reduce FWI, but increase TWI in both populations, and that privately owned cats have greater variability in drinking behavior due to environmental and routine heterogeneity. We also hypothesize that cats will drink less in the immediate postprandial period when provided with a high-moisture diet.

Materials and methods

Ethics

All procedures were approved by the University of Guelph Animal Care Committee (Study 1: AUP #5339 and Study 2: AUP #5408) and were in accordance with the Canadian Council on Animal Care (CCAC) and the Provincial Animals in Research Act.

Study 1: Water intake and drinking behavior in research colony cats

Animals and housing

This study was conducted from March to April 2025. Twelve neutered male domestic short-haired cats, aged 5–6 yr with a body condition score (BCS) of 4-6 and BW of 4.39 ± 0.38 kg (mean ± SD), housed in the Department of Animal Biosciences colony at the Ontario Agricultural College (Guelph, ON, Canada), were used in this study. Cats were deemed healthy based on their most recent physical exam and CBC biochemistry profile (4 mo prior to the study start). Cats were housed indoors in a free-living room (7.1 m × 5.8 m) equipped with elevated cat trees, perches, hiding boxes, enrichment structures, and soft bedding. Temperature and humidity were monitored continuously; temperature ranged from 24.2 to 25.2 °C (mean 24.6 ± 0.03 °C) and relative humidity from 18.7 to 43.1% (mean 25.0% ± 0.78). A 12-h light–dark cycle (lights on 0745–1945 h) was maintained. Cats received voluntary human interaction (brushing, petting, supervised play) for up to 2 h per day, 5 d per week. The room was cleaned and sanitized daily, and litter boxes were scooped twice daily.

Diets and study design

A within-subjects repeated-measures design was employed. Cats were transitioned from their previous diet (Ideal Solution for Adult cats, Nutram) for 6 d. Following the transition period, all cats sequentially received three dietary moisture treatments for 14 d each: 1) DRY: 100% dry diet (10% moisture; Acana Indoor Entrée Dry Cat Food, Champion Petfoods; Table 1), 2) MIXED: 63% moisture, 50% dry diet, and 50% wet food diet (10% moisture; Acana Indoor Entrée Dry Cat Food, Champion Petfoods; with 80% moisture; Acana Premium Paté, Beef Recipe, Champion Petfoods), and 3) WET: 100% wet food diet (80% moisture; Acana Premium Paté, Beef Recipe, Champion Petfoods) (Table 1). Cats were fed twice daily at 0800 and 1200 h in individual crates without access to water and were given up to 1 h to consume their meal. Refusals were recorded. Energy intake was held constant across treatments using isoenergetic feeding based on weekly BW measurements. After feeding, cats were released in pairs to prevent clustering at water stations.

Table 1.

Proximate analysis of Acana Indoor Entrée Dry Adult Cat Food (DRY), Acana Premium Paté Beef Recipe for Adult Cats (WET)

Nutrient	DRY	WET
Crude protein (min.), %	37.0	10.5
Fat (min.), %	14.0	7.0
Crude ash (max.), %	9.0	4.0
Crude fiber (max.), %	6.0	1.0
Moisture (max.), %	10.0	80.0
Calcium, %	1.3	0.5
Magnesium, %	0.1	0.3
Taurine, %	0.1	0.1
Phosphorus, %	1.0	0.3
ME, kcal/kg1	3533	1003

¹ME calculated according to the Nutrient Requirements of Dogs and Cats (NRC 2006)

These diets comply with the Association of American Feed Control Officials’ guidelines for adult cats at maintenance.

Dry diet: Ingredients: Fresh chicken (18%), chicken meal (16%), herring meal (15%), oat groats, whole peas, chicken fat (5%), ground miscanthus grass, whole green lentils, raw turkey (4%), raw whole herring (4%), whole chickpeas, whole red lentils, lentil fibre, raw rabbit (1%), fresh chicken giblets (liver, heart) (1%), raw turkey liver (1%), dried kelp, fresh whole butternut squash, fresh whole pumpkin, whole cranberries, whole blueberries, tocopherol extracts from vegetable oils, citric acid, rosemary extract, choline chloride, taurine: 400 mg, zinc proteinate, copper proteinate, vitamin B1, vitamin B2, vitamin B3, vitamin B5, vitamin B6, vitamin B9, vitamin B7, vitamin B12, vitamin A, vitamin D3, vitamin E, DL-methionine, L-carnitine, Enterococcus faecium DSM 10663/NCIMB 10415.

Wet diet: Ingredients: Beef, chicken, beef bone broth, beef liver, tuna, chicken bone broth, pumpkin, salmon oil, locust bean gum, taurine, tricalcium phosphate, potassium chloride, salt, vitamins [vitamin E supplement, thiamine mononitrate, niacin, vitamin A supplement, pyridoxine hydrochloride, calcium pantothenate, riboflavin supplement, folic acid, vitamin D3 supplement, biotin, vitamin B12 supplement], guar gum, minerals [magnesium sulfate, zinc amino acid chelate, iron amino acid chelate, copper amino acid chelate, manganese amino acid chelate, sodium selenite, potassium iodide], choline chloride.

Table 2.

Mean ± SD of free water intake, total water intake, duration and group, individual and total drinking events in 12 neutered male colony and 10 mixed sex privately (client)-owned domestic shorthair cats fed a 100% dry, 50% dry and 50% wet, or a 100% wet diet.

Variable	Study	Treatment			P-values
		Dry	Mixed	Wet
Free water intake (mL/d)	Colony	98.0 ± 34.7a	53.0 ± 24.5b	14.5 ± 15.3c	<0.001
	Client	98.2 ± 46.2a	71.6 ± 65.5b	36.5 ± 72.2c	<0.001
Total water intake (mL/d)	Colony	103 ± 34.7c	125 ± 25.0b	155 ± 20.6a	<0.001
	Client	104 ± 46.6a	140 ± 71.7b	169 ± 81.5c	<0.001
Duration (sec/d)	Colony	588 ± 316a	387 ± 250b	88.5 ± 107c	<0.001
	Client	629 ± 561a	413 ± 383b	150 ± 260c	<0.001
Drinking events (#/d)	Colony	5.80 ± 2.25a	4.20 ± 2.07b	1.60 ± 1.49c	<0.001
	Client	9.51 ± 4.36a	6.47 ± 4.25b	2.51c ± 2.44	<0.001
Individual drinking events (#/d)	Colony	3.79 ± 2.00a	2.90 ± 1.98b	1.47 ± 1.46c	<0.001
	Client	N/A	N/A	N/A	N/A
Group drinking events (#/d)	Colony	1.99 ± 1.50a	1.26 ± 1.09b	0.19 ± 0.45c	<0.001
	Client	N/A	N/A	N/A	N/A

^a,b,cLetters within the same row represent significance at P < 0.05.

N/A, not applicable

Water intake monitoring

Average FWI was defined as the amount of water the cat electively consumed daily. In contrast, average daily TWI was calculated to account for the diet’s moisture content, excluding metabolic water. Individual water intake was recorded using three Felaqua Connect Water Fountains (Sure Pet, ©2025 Merck & Co.Inc, Rahway, NJ, USA). The water fountains were set up according to the manufacturer’s instructions, connected to the WiFi connect hub, then positioned in three separate areas of the room. The research team validated the fountains before use in this study by observing the cat drinking from the fountain, recording the time spent drinking, and then verifying that the app correctly logged this information. Water volume, frequency, and duration of each drinking event for individual cats, identified via radio-frequency identification (RFID) microchip or RFID collar tags, were automatically uploaded to the PetSure App (SureFlap Ltd.). The water fountains were cleaned and refilled daily with distilled water. Cats were fitted with harnesses, and a RFID tag was secured to each harness. When multiple cats were observed drinking simultaneously from the fountain, the total volume consumed during each event was divided equally among the cats present to prevent overestimating individual water intake. Duration data were not adjusted. At the end of the research trial, the data were offloaded and stored on an encrypted, password-protected laptop for statistical analysis.

Study 2: Water intake and drinking behavior in privately owned cats

Animals and housing

This study was conducted from October to November 2025. Ten privately owned adult cats (n = 10; 5 neutered males, 5 spayed females) aged 1–5 yr with a BCS of 4-6 and a BW of 3.97 ± 0.79 kg were recruited through the University of Guelph community based on the following inclusion criteria: 1–10 yr of age, exclusively housed indoors, and the most recent veterinary records (within 1 yr of the study start date) confirming healthy clinical status. Owners were responsible for feeding and maintaining water-monitoring devices, with the principal researcher available to assist with technical issues. Cats must have been able to consume both formats of dry and wet food. Homes varied in layout, enrichment, temperature, humidity, and presence of other animals. Two female cats resided in the same household.

Diets and study design

A within-subjects repeated-measures design was employed. Cats were transitioned from their previous diet for 6 d. Following the transition period, all cats sequentially received three dietary moisture treatments, following the same format as study 1: 1) DRY: 100% dry diet, 2) MIXED: 50% dry and 50% wet diet and 3) WET: 100% wet food diet for 14 d each. Individual energy intake was not standardized; instead, it was matched to each cat’s normal daily food intake, as reported by owners. Pre-portioned feeding packages were prepared weekly by the researchers. Owners fed cats the pre-portioned food according to their habitual feeding schedules. Food refusals were collected weekly and weighed to calculate food intake. Owners were instructed to remove all other sources of food and water to ensure accurate calculations of water and food intake. Owners were also instructed to notify the research team of any deviations from the study protocol, including changes in water intake, feeding behavior, or health status, throughout the study period.

Water intake and monitoring

Individual water intake was measured using either a Felaqua Connect water fountain (Sure Petcare, Merck & Co., Inc., Rahway, NJ, USA) in multi-pet households following the same directions above or a Dockstream water fountain (Petlibro, San Jose, CA, USA) in single-pet households. Owners were instructed to clean and refill fountains every 2 to 3 d using fresh water and to avoid harsh soaps or detergents. All data were automatically transmitted to the PetSure (SureFlap Ltd.) or Pet Libro (Petlibro) App, then uploaded to an encrypted, password-protected account managed by the researchers. Owners were asked to maintain consistent feeding and watering locations and schedules throughout the study period to minimize environmental variation. When multiple pets drank simultaneously from the smart water drinkers, the total volume consumed during each event was divided equally among the cats present to avoid overestimating individual intake. The duration of drinking was not adjusted, as in the colony study.

Data processing and variable construction

Raw event-level data (timestamp, duration, volume per drinking event) from smart fountains were aggregated into daily measures for each cat and dietary treatment using R (dplyr package). The following variables were calculated:

$$\begin{array}{l}\text{FWI} \left(\text{mL}/\text{day}\right)=\text{sum} \text{of} \text{voluntarily} \text{consumed} \text{water}\\ \text{FOOD} \text{WATER} \left(\text{mL}/\text{day}\right)=\text{dietary} \text{moisture} \text{intake} \text{based} \text{on} \text{ME} \text{and} \text{diet} \text{composition}\\ \text{TWI} \left(\text{mL}/\text{day}\right)=\text{FWI}+\text{FOOD} \text{WATER}\\ \text{TOTAL} \text{DURATION} \left(\mathrm{s}/\text{day}\right)=\text{sum} \text{of} \text{all} \text{drinking} \text{event} \text{durations}\\ \text{AVERAGE} \text{DURATION} \left(\mathrm{s}/\text{event}\right)=\text{mean} \text{duration} \text{per} \text{drinking} \text{event}\\ \text{FREQUENCY} \left(\text{events}/\text{day}\right)=\text{total} \text{number} \text{of} \text{drinking} \text{events}\end{array}$$

For the privately owned cat dataset, a DAY variable was assigned to standardize timelines across cats with staggered start dates.

Statistical analysis

All statistical analyses were performed in R (v. 4.4.1; R Core Team, Vienna, Austria). For both studies 1 and 2, descriptive statistics (mean ± SD) were calculated for FWI, TWI, total drinking duration, drinking duration per event, and number of drinking events. Because all outcomes exhibited right-skewed distributions, linear mixed-effects models were fitted using the lmer function from the lme4 package, with log or log1p transformations applied as appropriate to satisfy model assumptions. For each outcome, dietary treatment was included as a fixed effect, and individual cats were included as a random intercept to account for repeated measures across days. Model assumptions were evaluated using residual-vs.-fitted plots and normal Q–Q plots. When assumptions were met, estimated marginal means, which account for covariation and unbalanced data (Searle et al. 1980), were obtained using the emmeans package. To evaluate drinking patterns, the fed periods were defined from 0800 to 1000 h and 1200 to 1400 h, corresponding to the two daily feeding times at 0800 and 1200 h. All other hours were considered fasted periods. The analysis was based on repeated measures of time, with cats nested within each period, with day as the unit of analysis. The effects of diet, time, day, and the interaction between diet and time were evaluated, and all model assumptions were assessed through residual analysis. For all analyses, significance was declared at P < 0.05, and Tukey pairwise adjustments were performed when significant.

To compare drinking behavior between colony-housed and privately-owned cats, datasets from studies 1 and 2 were merged after aligning variable structures and scaling. A second set of linear mixed-effects models was fitted, including dietary treatment, environment (colony vs. privately owned), and their interaction as fixed effects, with individual cats included as a random effect. Estimated marginal means and Tukey-adjusted contrasts were computed for all relevant environment × treatment comparisons. Because one cat (“SAM”) participated in both studies, an additional exploratory within-individual comparison was conducted to descriptively compare SAM’s drinking behavior across colony and home environments. These results are presented as means and standard deviations without formal inference due to the single-animal nature of this comparison (Table S2).

Results

Study 1: Water intake and drinking behavior in research colony cats

In general, FWI decreased with increasing dietary (food) moisture (Figure 1). Cats on the DRY diet had a greater FWI than those on the WET and MIXED diets, and on the MIXED diet than on the WET diet (P < 0.001). Conversely, cats on the WET diet had a greater TWI than cats on the DRY and MIXED diets, and on the MIXED diet than the DRY diet (P < 0.001) (Table 2). The time spent drinking (s) decreased, as dietary moisture increased (P < 0.001). Similarly, the total number of drinking events, including both individual and group events, decreased with increasing dietary moisture (P < 0.001; Table 2). Across all three treatments, cats drank more free water during the fed period compared to the fasted period (P < 0.001; Table 3).

Figure 1.

Comparison of dietary moisture (mL) and free water intake (mL) in 12 colony domestic shorthair cats (n = 12) across three experimental diets (100% dry, 50% dry and 50% wet, or 100% wet). ^a,b,cDifferent letters indicate significant statistical differences in total water intake, P < 0.05.

Table 3.

Mean ± SD of free water intake between experimental diets (100% dry, 50% dry and 50% wet, or a 100% wet) in the fasted vs. fed state in 12 colony neutered domestic shorthair cats. The fed state was defined as 0800–1000 h and 1200–1400 h, and the fasted state as all other times of the day.

Treatment	Period		P-values
	Fasted	Fed	Trmt	Prd	Trmt × Prd
Dry	29.1 ± 21.7a	69.0 ± 31.7a	<0.001	<0.001	<0.001
Mixed	14.2 ± 15.8b	38.0 ± 18.8b
Wet	4.73 ± 8.70c	9.68 ± 11.1c

^a,b,cLetters within the same row represent significance at P < 0.05.

Study 2: Water intake and drinking behavior in privately owned cats

Similar results to those of study 1 were found in study 2 (Figure 2). Cats on the DRY diet had a greater FWI than those on the WET and MIXED diets, and on the MIXED diet than on the WET diet (P < 0.001). Conversely, cats on the WET diet had a greater TWI than cats on the DRY and MIXED diets, and on the MIXED diet than the DRY diet (P < 0.001; Table 2). The time spent drinking (s) decreased, as dietary moisture increased (P < 0.001). Similarly, the total number of drinking events, including both individual and group events, decreased with increasing dietary moisture. Total daily drinking duration decreased with increasing dietary moisture (P < 0.001). The total number of drinking events followed a similar pattern, decreasing with increasing dietary moisture (P < 0.001). Average drinking duration was greater when cats were fed the DRY or MIXED diet than the WET diet (P < 0.001), but they did not differ from each other (Table 2).

Figure 2.

Comparison of dietary moisture (mL) and free water intake (mL) in 10 privately owned domestic shorthair cats (n = 12) across three experimental diets (100% dry, 50% dry and 50% wet, or 100% wet). ^a,b,cDifferent letters indicate significant statistical differences in total water intake, P < 0.05. Graph on water intake of colony domestic shorthair male cats fed a dry, mixed, or wet diet whereby a, b, and c denote statistical significance.

Comparison of colony and privately owned cats across dietary treatments

Privately owned cats drank more free water than colony cats fed the same DRY, MIXED, and WET diets (P < 0.001 for all comparisons). Privately owned cats also consumed more total water than colony cats fed the same DRY, MIXED, and WET diets, respectively (P < 0.001 for all comparisons; Table 4). A strong positive correlation was observed between mean daily FWI in colony and privately owned cats (r = 0.872, P < 0.001; Figure 3). Daily TWI showed a similarly strong correlation (r = 0.788, P < 0.001; Figure 4). Total daily drinking duration was greater in privately owned cats than colony cats fed the DRY (337.5 s/d, P = 0.011) and MIXED (184.6 s/d, P = 0.019) diets, but not when fed the WET diet (P = 0.93). Average duration per drinking event did not differ between privately owned and colony cats fed the DRY (P = 0.47) or MIXED (P = 0.79) diets. Privately owned cats had shorter average drinking events than colony cats when fed the WET diet (6.4 s/event, P = 0.011; Table 4).

Table 4.

Estimated marginal means (back-transformed log1p) and client-owned-to-colony contrasts for water intake outcomes across dietary treatments.

Variable	Trmt	Colonya	Clienta	Difference (client—colony)	P-values
Total water intake (mL/day)	Dry	79.5	117.1	+37.6	<0.001
	Mixed	100.5	155.1	+54.6	<0.001
	Wet	125.6	190.0	+64.4	<0.001
Free water intake (mL/day)	Dry	48.9	172.1	+123.2	<0.001
	Mixed	24.8	98.7	+73.9	<0.001
	Wet	3.5	11.4	+7.9	<0.001
Total duration (sec/day)	Dry	335.4	672.9	+337.5	0.011
	Mixed	206.6	391.2	+184.6	0.019
	Wet	19.4	19.0	ns	0.93
Average duration (sec/event)	Dry	75.4	65.0	ns	0.47
	Mixed	66.1	62.5	ns	0.79
	Wet	14.7	8.3	–6.4	0.011

^aEstimated marginal means back-transformed from mixed models fitted using a log1p transformation. As such, values correspond to geometric mean predictions on the original scale and may differ from raw numerical averages. Confidence intervals and contrasts are also presented on the back-transformed scale.

trmt, treatment; ns, non-significant.

Figure 3.

Pearson correlation between daily mean free water intake (mL/day) in colony-housed cats and privately owned cats across the 42-day dietary moisture study (r = 0.872, P < 0.0001).

Figure 4.

Pearson correlation between colony and privately owned cats for total water intake (mL/day) across the 42-day dietary moisture study (r = 0.788, P < 0.0001).

Discussion

These studies support the conclusion that dietary moisture is a primary driver of FWI of both privately owned and research colony cats. In the current study, cats achieved the highest TWI when fed the 100% wet diet, despite having the lowest FWI. In contrast, FWI was highest when cats were fed the 100% dry diet, with the mixed diet as an intermediate. Similar results have been reported in previous studies of research colony cats (Kane et al. 1981; Carciofi et al. 2005; Buckley et al. 2011; Thomas et al. 2017) and, more recently, senior (7+ yr) cats in at-home environments fed ad libitum (Eyre et al. 2025). While conducting long-term longitudinal studies in cats with low water intake is challenging, evidence suggests that chronic underhydration and elevated USG contribute to the development of urinary tract diseases. Previous research reports that cats fed a dry diet have a 2.64-fold higher risk of developing feline lower urinary tract disease than those fed a mixed diet (Piyarungsri et al. 2020). In additional studies, cats fed an exclusive dry diet had a 6.90-fold greater risk of urologic syndrome or a 15.87-fold greater risk of urethral obstruction than when fed an exclusively canned diet (Willeberg 1984; Kennedy and White 2022). These results could be attributed to lower water intake, as observed in the current study, suggesting that cats fed dry diets may not consume sufficient free water to maintain their hydration state.

In the present study, when directly comparing colony-housed and privately owned cats, mean daily FWI and TWI were strongly correlated across the 42-day study period, indicating that drinking patterns were preserved across housing contexts despite variation in age, BW, and sex. Previous research in a colony of 35 mixed-sex cats reports that the presence of a familiar human increases feeding frequency compared with the absence of that person (Damasceno et al. 2016). Given that privately owned cats consumed more water and drank more frequently than colony cats (Table S3), the current study may have captured the same effect in drinking behavior; however, further investigation is required. Despite differences in magnitude, drinking patterns between colony- and privately owned cats were similar, indicating that responses to dietary moisture were conserved across housing environments. Together, these findings indicate that while absolute water intake may differ between controlled and home settings, the directional effects of dietary moisture are consistent, supporting the external validity of controlled colony studies for predicting hydration responses in privately owned cats.

Importantly, the fat and protein content, as well as ingredient composition, differed among the diets; thus, macronutrient composition, in addition to moisture content, may have influenced drinking patterns. Previous work has reported a higher FWI and/or TWI in cats fed a soy-based, high protein (up to 64%), or high salt diet than cats fed a starch based (Mendonça et al. 2018), low protein (29% or less) (Hashimoto et al. 1995), or low salt diet (11.51–16.74 g Na/MJ) (Hawthorne and Markwell 2004), respectively. Conversely, Garcia et al. (2021) reported similar FWI and TWI in cats fed diets with 39.0% or 52.0% crude protein on a dry matter basis (DMB), with similar fat content; however, FWI and TWI of cats on diets with 28% and 64% protein differed. Collectively, these findings suggest that dietary protein may influence water intake primarily when differences in protein concentration are substantial. Thus, the difference in protein content between the two diets should be noted. In the present study, the WET diet provided an estimated 52.5% crude protein an 35.0% fat on a DMB, compared to 45.6% and 23.2% DMB, respectively, on the MIXED diet, and 41.1% and 15.6% DMB, respectively, on the DRY diet (Table S1). Despite the higher protein content, cats on the WET diet consumed less free water, suggesting that dietary moisture, rather than diet composition, had a greater influence on FWI in the current study. Dietary fat content does not appear to affect water intake (Kane et al. 1987; Carciofi et al. 2005), though research is limited.

In the present study, a brief increase in FWI and TWI was observed during the first 24 h after each dietary transition, followed by a return to baseline levels (Figures S1–S4). This brief adjustment period suggests a rapid response to changes in dietary moisture content. Similar short-term 24-h persistence of drinking behavior following diet transitions has been described, whereby cats continued drinking immediately after being switched from dry to high-moisture diets, before voluntary intake declined (Kane et al. 1981). This timed pattern was observed in both controlled colony conditions and heterogeneous home environments, indicating that dietary moisture exerted a stronger influence on hydration behavior than environmental variability. These findings suggest that single-day measurements may not adequately capture feline hydration behavior and highlight the importance of multi-day intake assessment when evaluating dietary or environmental effects on water consumption (Figures S5 and S6).

There is a dearth of knowledge on how changing the composition of a cat’s diet can impact the time of day during which they choose to drink. Contrary to our third hypothesis, results suggest that cats drink more water in the immediate postprandial state (within 2 h of meal consumption), regardless of the diet’s moisture content. To the author’s knowledge, this is the first study to investigate FWI in relation to the fed vs fasted state in cats. Previous research reports that cats prefer to eat at dawn and dusk when given the choice (Parker et al. 2022); however, in this study, mealtimes were provided at 0800 and 1200 h, suggesting that increased water intake is associated with food intake rather than with crepuscular influences. These results suggest that stomach-capacity signals did not deter cats from drinking after a meal, as hypothesized by Wyrwicka (1978). Additionally, it was noted that when group drinking events occurred (multiple cats drinking from the same source simultaneously), they often involved the same individuals. This suggests that the social structure may also affect when colony-housed cats drink and which water source they choose. While the effects of social behavior on water intake in cats have not yet been investigated, previous research indicates that younger, smaller, and female individuals typically gain access to food before older, larger males (Bonanni et al. 2007). This pattern may extend to other shared resources, such as water. Interestingly, the same pattern has been observed in lemurs, which follow a matriarchal (female-dominant) system, with juveniles or females drinking before males (Fornasieri et al. 1993). However, in cows, dominance positively impacts the duration and number of drinking events (Coimbra et al. 2012; Nizzi et al. 2024). Future studies on feline hydration should investigate the social contexts in which drinking events occur, and whether any individuals are discouraged from drinking due to the presence or behavior of others.

There were important limitations to this study. Firstly, due to the fountain’s recording system, the duration of drinking events may have been inflated in colony cats and in privately owned multi-cat households during periods of group drinking. In such instances, each cat’s drinking event was recorded as the maximum duration the bowl was accessed during a group drinking bout, rather than the actual time spent drinking by each individual. Additionally, the total volume of water consumed during a group drinking event was initially attributed to all cats present, thereby inflating estimates of individual intake. To address this, the total FWI for group drinking events was divided equally among all drinking cats and assigned accordingly. Although the precise volume consumed by each cat cannot be determined, this approach reduced the inflation of FWI in individual cats. While evaporation has been accounted for in previous studies using inaccessible control water sources (Grant 2010; Pachel and Neilson 2010; Robbins et al. 2019; Hall et al. 2021), such methods are themselves sensitive to fluctuations in ambient temperature and humidity. Given that the fountain system records changes in water volume only during active drinking events when an RFID is detected, any contribution of evaporation in the present study is expected to be minimal. Additionally, the repeated-measures design, with a sequential diet order, introduced limitations. While this design allowed us to assess how rapidly cats altered water intake behaviors in response to increasing dietary moisture, the period was confounded by diet, which may have influenced the interpretation of treatment effects over time.

Conclusion

These data provide novel evidence of the effects of dietary moisture content on the timing of FWI in cats and validate findings from a controlled colony study in a privately owned, free-living population. Our results in healthy cats also support that cats fed a dry, low-moisture diet have higher FWI but lower TWI than those fed a wet, high-moisture diet. Finally, our data suggest that cats prefer to drink when fed, near mealtimes, rather than at other times of the day. Future researchers should focus on how various characteristics (e.g. sex, body fat, age) influence water and food intake in cats.

Glossary

Abbreviations

BW

body weight

FWI

free water intake

RFID

radio frequency identification

TWI

total water intake

Author contributions

Ryan Van Diggelen (Data curation, Formal analysis, Investigation, Visualization, Writing—original draft), Genevieve Gillies (Data curation, Formal analysis, Investigation, Visualization, Writing—original draft), Pauline Angela Louise Kosmal (Conceptualization, Investigation, Methodology, Supervision, Validation, Writing—review & editing), and A.K. Shoveller (Conceptualization, Funding acquisition, Methodology, Supervision, Validation, Writing—review & editing), and Sydney Banton (Methodology, Validation, Writing—review & editing)

Supplementary data

Supplementary data is available at Journal of Animal Science online.

Funding

This work was funded by Peturio LLC, DBA Cat Years. However, this financial support did not influence the conduct of this study or the interpretation of the data.

Conflict of interest statement. Rv.D., G.G., S.B., and P.A.L.K. declare no conflict of interest with respect to the research, authorship, and/or publication of this article. A.K.S. has received honoraria and research funding from various pet food manufacturers, ingredient suppliers, and provincial and federal granting agencies. They declare that they serve on the Scientific Board of Champion Petfoods.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.