Seasonal variation in the amount of dietary carbohydrate not absorbed from the intestine after breakfast in elderly Japanese females

It was previously shown that there is seasonality in the amount of dietary carbohydrate not absorbed from the intestine after breakfast, the amount of carbohydrate in winter being significantly larger than that in autumn in young Japanese subjects. In order to investigate this phenomenon further, the experiment was repeated on 22 elderly Japanese female subjects (61-78 yrs of age) during the four seasons of the year. The amount of unabsorbed dietary carbohydrate by the breath hydrogen test, which measures the amount of hydrogen in exhaled air, was then esitmated. A 6 g solution of lactosucrose, an indigestible trisaccharide, was used for comparison. Two groups of subjects, 16 subjects in Osaka and 6 subjects in Nagano, were studied in the summer (July to August) and autumn (October to November) of 2005 and the winter (January to February) and spring (April to May) of 2006. The following results were found using the pooled data of the total of 22 subjects. With regard to the amount of breath hydrogen excretion of the lactosucrose solution, there was no significant difference between the four seasons. There was a significant seasonal change in the efficiency of dietary carbohydrate absorption from the intestine after breakfast. The percentage of total carbohydrate that was not absorbed was lowest in the spring and highest in the winter. A comparison of the results from studies on the elderly and young subjects revealed the percentage of total carbohydrate that was not absorbed in the elderly was significantly lower than in the young in the winter, spring, and summer. These results indicate that there is seasonal variation in the efficiency of dietary carbohydrate absorption from the intestine among elderly female Japanese subjects as well as young female Japanese subjects. They also suggest that the efficiency of dietary carbohydrate absorption from the intestine after breakfast is retained in these naturally active and healthy elderly subjects.     

Seasonal Variation in Amount of Unabsorbed Dietary Carbohydrate from the Intestine after Breakfast in Japanese Subjects

We previously showed that daytime dim‐light exposure has a negative effect on the efficiency of dietary carbohydrate absorption in the evening, whereas evening‐time dim‐light exposure has a beneficial effect. These results suggest that seasonal changes in the environmental light may affect gastrointestinal activity, and that there might, therefore, be seasonal variation in the efficiency of dietary carbohydrate absorption from the intestine. In order to prove this hypothesis, we measured the amount of dietary carbohydrate unabsorbed from the intestine after a breakfast in healthy female Japanese subjects during the four seasons of the year. We estimated the amount of unabsorbed dietary carbohydrate by the breath hydrogen test, which measures the amount of hydrogen in exhaled air. A 6 g solution of lactosucrose, an indigestible trisaccharide, was used for comparison. Two groups of subjects, 12 subjects in Osaka and 14 subjects in Nagano, were studied in the winter (January to February), spring (April to May), summer (July to August), and autumn (October to November) of 2004. We found the following results: (1) In no season were there any significant differences between the two subgroups in the orocecal transit time of the breakfast and the lactosucrose solution. Nor were there any significant differences in the amount of unabsorbed dietary carbohydrate from the breakfast. (2) Using the pooled data of the total of 26 subjects, there was no significant seasonal variation in the orocecal transit time of the breakfast or the lactosucrose solution. (3) There was a significant seasonal variation in the amount of unabsorbed dietary carbohydrate from the breakfast. (4) The amount of unabsorbed dietary carbohydrate from the breakfast was largest in winter and smallest in autumn. Results in spring and in summer were similar and intermediate between those in winter and autumn. Post hoc multiple comparison tests showed that the amount of unabsorbed dietary carbohydrate in winter was significantly larger than in autumn. (5) In winter, the average ratio of the amount of unabsorbed dietary carbohydrate to the total amount of carbohydrate in the breakfast was about 12%; in autumn it was about 6%. These results clearly show that there is seasonal variation in the efficiency of intestinal dietary carbohydrate absorption among young female Japanese subjects.     

Seasonal Variation in the Amount of Dietary Carbohydrate Not Absorbed from the Intestine after Breakfast in Elderly Japanese Females

It was previously shown that there is seasonality in the amount of dietary carbohydrate not absorbed from the intestine after breakfast, the amount of carbohydrate in winter being significantly larger than that in autumn in young Japanese subjects. In order to investigate this phenomenon further, the experiment was repeated on 22 elderly Japanese female subjects (61–78 yrs of age) during the four seasons of the year. The amount of unabsorbed dietary carbohydrate by the breath hydrogen test, which measures the amount of hydrogen in exhaled air, was then esitmated. A 6 g solution of lactosucrose, an indigestible trisaccharide, was used for comparison. Two groups of subjects, 16 subjects in Osaka and 6 subjects in Nagano, were studied in the summer (July to August) and autumn (October to November) of 2005 and the winter (January to February) and spring (April to May) of 2006. The following results were found using the pooled data of the total of 22 subjects. With regard to the amount of breath hydrogen excretion of the lactosucrose solution, there was no significant difference between the four seasons. There was a significant seasonal change in the efficiency of dietary carbohydrate absorption from the intestine after breakfast. The percentage of total carbohydrate that was not absorbed was lowest in the spring and highest in the winter. A comparison of the results from studies on the elderly and young subjects revealed the percentage of total carbohydrate that was not absorbed in the elderly was significantly lower than in the young in the winter, spring, and summer. These results indicate that there is seasonal variation in the efficiency of dietary carbohydrate absorption from the intestine among elderly female Japanese subjects as well as young female Japanese subjects. They also suggest that the efficiency of dietary carbohydrate absorption from the intestine after breakfast is retained in these naturally active and healthy elderly subjects.     

Seasonal variation in gastric myoelectrical activity in young Japanese females

In order to test our hypothesis that there is seasonal variation in digestion and absorption of dietary carbohydrate from the intestine, we previously determined the amount of unabsorbed carbohydrate after breakfast by the breath hydrogen test in the four seasons. In pursuing our hypothesis further, we also recorded gastric myoelectrical activity before and after the breakfasts. In the current report, we describe the seasonality of gastric myoelectrical activity. Twenty-six Japanese female subjects were studied in winter, spring, summer and autumn. The cutaneous electrogastrogram was analysed by spectral analysis to compute the pre- and post-prandial dominant slow wave frequency (DF), and percentage of the 2 - 4 cpm gastric slow wave (Normal %). Two-factor ANOVA indicated that there was no significant seasonal variation in DF and Normal %. These results indicate that seasonal variations in digestion and absorption of dietary carbohydrate are caused by factors other than gastric and small intestinal motility.     

Effects of a late supper on digestion and the absorption of dietary carbohydrates in the following morning

Background

Our previous experiment showed that the light intensity exposed on the subjects during evening time had no effect in the following morning on the efficiency of the digestion and absorption of dietary carbohydrates ingested at a usual suppertime. People who keep late hours usually have a late suppertime; thus, we examined the effects of a late suppertime on gastrointestinal activity in the following morning in comparison to that of a usual suppertime.

Methods

Twelve female university students volunteered as paid participants. The breath hydrogen test was carried out to estimate the amount of unabsorbed dietary carbohydrates and the percentage of the total amount of dietary carbohydrates in the breakfast that were unabsorbed, as well as to estimate oro-cecal transit time. The respiratory quotient was also measured to find the ratio of carbohydrates/lipid metabolism in the post-breakfast state. Subjects’ peripheral blood glucose concentration was measured by a blood glucose meter. The subjects participated under two different experimental conditions: with a usual suppertime (having supper at 18:00) and a late suppertime (having supper at 23:00).

Results

The efficiency of the digestion and absorption of dietary carbohydrates in the breakfast under late suppertime conditions was higher than that under usual suppertime conditions. Usual or late suppertime had no effect on the ratio of carbohydrates to lipids oxidized after the subjects had breakfast. There were significant differences in the blood glucose level between the two conditions at 30, 60, 120, 150, and 180 minutes after having breakfast, whereas the mean blood glucose level under late suppertime conditions was significantly higher than under usual suppertime conditions.

Conclusions

Having a late supper showed a worse effect on postprandial serum glucose profiles the following morning. This study confirmed that keeping our usual meal timing is important for our health.     

Seasonal variation of vesicular-arbuscular mycorrhizae in eroded soils from southern Spain

A survey was carried out of the seasonal variations in the number of spores in the soil and of the percentage of root infection. The stage of development of the host plants, environmental variations and physicochemical characteristics of the soil were taken into account. Fifteen plants valid as forage and adaptable to semi-arid conditions and poor soils were selected. In general, the maximum spore density was reached in the fruit-bearing period of the plants. It remained high during autumn, fell to a minimum in winter and tended to increase in spring. Root infection was at a maximum when the plants flowered, after which it decreased to a minimum in summer.     

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.     

Seasonal variation of the chemical constituents of the essential oil of Santolina etrusca from Italy

The seasonal variation of the essential oil, in terms of both yield and composition, of a population of Santolina etrusca (Asteraceae) is reported in detail for different aerial parts, including sterile branches, fertile branches, and capitula. The yields generally increased from November to June, and then decreased in August and September. The main constituents of the sterile branches were 1,8-cineole and viridiflorol. The oil from fertile branches was characterized by myrcene as principal compound, whereas the essential oil obtained from the capitula contained germacrene D as the main constituent. Several compounds, as identified by GC and GC/MS, were found to prevail during the cold season.     

Seasonal variation of denitrification rate in Lake Suwa sediment

The seasonal variation of denitrification rate in sediments in the central station of Lake Suwa, Japan, was estimated by the acetylene-inhibition technique from March 20 to December 10, 1994. The denitrification rate ranged from 0 to 1800µmolNm^–2day^–1 and showed a distinct seasonal trend, i.e., relatively high rates in spring and winter, and low or negligible rates in summer. The denitrification rate was well correlated with NO^–₃ concentration in overlying water, suggesting that NO^–₃ in overlying water was the primary controlling factor for denitrification. The annual rate of denitrification was 0.15molNm^–2year^–1. Denitrification removed 5% of the annual nitrogen load from the lake, and this fraction was relatively small compared to the values reported for a variety of aquatic environments. In Lake Suwa, NO^–₃ in the water column was depleted during summer, and this suppressed effective removal of nitrogen from the lake by denitrification.     

不同龄林华山松非结构性碳水化合物季节变化

【目的】探究不同龄林华山松NSC及其组分随季节变化在各器官的分配,对于揭示不同龄林华山松的碳分配机制有重要意义。【方法】以幼、中龄林华山松为研究对象,通过周期性采样,测定不同龄林华山松不同器官NSC及其组分含量,以探究其年内季节动态变化。【结论】结果表明：（1）不同龄林华山松植株NSC及其组分在各器官间的分配规律基本一致,表现为淀粉含量根>叶>枝>茎,茎中淀粉含量显著低于其他器官,可溶性糖和NSC在叶、根、枝中含量差异不明显;茎中糖淀比显著低于其他器官。（2）在整个生长季内,华山松NSC及其组分主要受季节影响,季节×器官间交互作用对它们的影响次之,林龄对它们的影响最小。（3）在不同龄林中各器官NSC及其组分之间的相关性基本一致,除幼龄林糖淀比与淀粉、NSC,中龄林糖淀比与淀粉为负相关外,其余指标之间为正相关。【结果】综上所述,华山松各器官NSC及其组分含量存在明显的季节波动,当环境变化时不同器官间的碳供需协同变化,有利于华山松生长,并增强其应对极端环境的抵抗力和适应性。     

Seasonal and age-related variation in the needle quality of five conifer species

Summary Age changes of foliage resource quality (water, nitrogen, fibre, phenolics and toughness) were studied in five species of conifer (Pinus sylvestris L.), Picea abies (L.) Karsten, Tsuga heterophylla (Rafinesque) Sargent (all Pinaceae), Chamaecyparis lawsonian (Murray) Parlatore and Thuja plicata D. Don (both Cupressaceae) over a 2-year period in an English forest.Mature foliage of Pinus sylvestris was characterized by higher levels of nitrogen, fibre and toughness, and lower phenolics, and that of Tsuga heterophylla by higher levels of phenolics, and lower fibre and toughness levels, than the mature needles of the other species studied. Immature needles had higher levels of water and nitrogen, and lower levels of fibre and toughness, than older needles. Immature needles of Picea abies and Tsuga heterophylla had a high concentration of phenolics, which decreased with needle maturity. By mid-August, the levels of most of the foliar constituents in current-year needles had stabilized at levels maintained for the next year. Sampling revealed a fall in the concentration of phenolics, fibre and water in mature needles between March and June. Possible reasons for this seasonal trend are discussed. The levels of conifer foliar constituents were compared with levels recorded in broadleaf trees. Conifers had greater concentrations of all measured foliar constituents, but, with the exception of the six fold greater toughness of conifer needles, the differences between broadleaves and conifers were less than those between the immature and mature conifer needles. Previous studies have related the abundance of Lepidoptera on conifers to hostplant taxonomic relationships. However, the foliar constituents measured in this study were poor predictors of taxonomic relationships between the conifers. It is suggested that the abundance of Lepidoptera on conifers is not determined by levels of general foliar constituents and the role of other hostplant factors in shaping lepidopteran utilization of conifers is discussed.     

Seasonal variation of dissolved aluminum concentration in harmonic-type Lake Biwa, Japan

Monthly observations performed on a typical harmonic-type lake, Lake Biwa (latitude 35°15′ N, longitude 136°05′ E, Japan), showed that the particulate aluminum concentration varied around a mean value of 0.8 μM, with occasional extraordinarily high values, whereas the dissolved aluminum concentration varied, in the surface layer of the whole lake, between a minimum of 0.01 μM and a maximum of 0.30 μM, depending on the season. Although the variation in dissolved aluminum paralleled the variation in the pH of the lake water, the variation in dissolved aluminum lagged behind the variation in pH by approximately 1 month. A series of laboratory incubation experiments suggested that the supply of dissolved aluminum from, and its removal by, the suspended particulate matter involved a slow, pH-dependent reaction. The stoichiometry and the apparent equilibrium constant of this reaction were evaluated by adopting a zeolite-like structure for the surfaces of the suspended particulates. Received: December 28, 2000 / Accepted: August 22, 2001     

Seasonal variation in primary production of microphytobenthos at the Isshiki intertidal flat in Mikawa Bay

Seasonal variations in photosynthetic rates by microphytobenthos and phytoplankton at the Isshiki tidal flat in Mikawa Bay were measured with a ¹⁴C combustion method. In addition, diurnal variations in the photosynthetic rate and photosynthesis versus irradiance (P-I) curves were obtained through in situ incubation. The photosynthetic rate of microphytobenthos (annual average, 13.9 ± 6.4 mg C m⁻² h⁻¹) did not show a remarkable change, and they maintained a higher production rate than phytoplankton (annual average 9.0 ± 5.1 mg C m⁻² h⁻¹) throughout the year. The P-I curves from in situ experiments showed that the photosynthetic activity of microphytobenthos at the laboratory irradiance (250 μE m⁻² s⁻¹) was 56% of that at the maximum irradiance (1200 μE m⁻² s⁻¹) in situ. In the in situ experiments, the chlorophyll a concentration, photosynthetic rate, and activity of microphytobenthos varied greatly throughout the day, influenced by tidal submersion/emersion and daylight. From an analysis of these results, it is considered that microphytobenthos contributed greatly to primary production in this ecosystem throughout the year by adapting suitably to intertidal environments. Received: July 28, 1999 / Accepted: October 10, 1999     

黄喉貂日活动节律及食性的季节变化

2016年4月至2017年4月,采用红外相机技术和粪便分析法(频率法和剩余物干重法)对四川栗子坪国家级自然保护区内黄喉貂不同季节的日活动节律及食物组成变化进行了研究。结果显示:(1)黄喉貂主要在白天活动(昼间独立照片数占总独立照片数的85. 64%),不同季节黄喉貂日活动节律无显著差异(χ~2=126. 950,df=132,P=0. 608),但在不同季节其日活动高峰出现时间不同,春季的活动高峰在16:00~19:00(31. 65%),夏季活动高峰在15:00~18:00 (26. 32%),秋季活动高峰在13:00~16:00 (34. 31%),冬季活动高峰在11:00~14:00 (25. 00%),并且冬季夜间活动与其他季节相比明显增多;(2)黄喉貂取食食物有兽类、鸟类、昆虫类和植物类等,但兽类是黄喉貂最主要的食物来源,在一年中以兽类的出现频率最高,为95. 28%,兽类剩余物的总相对干重百分比达80. 99%,其次是植物、鸟类和昆虫;(3)黄喉貂对食物类别的利用表现出明显的季节差异,春、夏、秋三个季节黄喉貂粪便中兽类所占比重最多,春季鸟类出现频率较高,冬季黄喉貂粪便中植物所占比重明显增多。本研究表明,黄喉貂在不同季节其日活动节律和食性均表现出一定的差异,这可能与其繁殖特性和生理代谢需求有关。本研究揭示了黄喉貂的日活动节律及食性的季节性变化,充实了黄喉貂的生物、生态学资料,也为该物种的保护管理提供了参考资料。     

Seasonal and intradiurnal variation of allergenic fungal spores in urban and rural areas of the North of Portugal

Because fungal spore emission intensity varies throughout the year and even throughout the day, study of the hourly distribution is an important aspect of aerobiological monitoring. The objective of this work was to determine seasonal and intradiurnal variation of allergenic airborne fungal spores in urban and rural areas. The aerobiological study was performed from 2005 to 2007 using Hirst-type volumetric spore traps. Fungal spore types (Cladosporium, Alternaria, and Aspergillus/Penicillium) were selected according to their allergenic capacity and their frequency in the atmosphere. Cladosporium was the most frequent fungal spore in both locations, together with Alternaria; its concentration was higher during summer whereas Aspergillus/Penicillium was more abundant during autumn. Alternaria and Cladosporium maximum daily spore concentration was reached from 16.00 to 20.00 h. Aspergillus/Penicillium spore distribution differed in the two locations, and although it was difficult to establish a distribution pattern the highest concentration were found during the night. Determination of periods of high concentration may help allergic patients to avoid the daily periods when the allergen concentration is highest.     

Seasonal variation in antimicrobial and phytochemical properties of frequently used medicinal bulbous plants from South Africa

The growing popularity of traditional medicine and the unrestricted collection of medicinal plants from the wild have put many of the slow growing bulbous plant species at the risk of over-exploitation and extinction in South Africa. This study was aimed at comparing the phytochemical composition and biological (antibacterial and anticandidal) activities of bulb and leaf extracts of Tulbaghia violacea, Hypoxis hemerocallidea, Drimia robusta and Merwilla plumbea between spring, summer, autumn and winter seasons, with the view of promoting the use of leaves, as a conservation strategy. Antibacterial and anticandidal activities of petroleum ether (PE), dichloromethane (DCM), 80% ethanol and water extracts of bulbs and leaves were tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae bacteria and the fungus Candida albicans using the microdilution bioassay. Spectrophotometric methods were used to evaluate saponin and phenolic compositions for the four seasons. Leaf and bulb extracts exhibited comparable anticandidal activity (MIC < 1 mg/ml) in all the plant species in all seasons. Only ethanol and water extracts of H. hemerocallidea corms (autumn and winter) showed correspondingly good fungicidal activity amongst the bulbs tested. Antibacterial activity was fairly comparable between bulbs and leaves with at least one extract of each plant species showing some good MIC values in most of the seasons. The best antimicrobial activities were recorded in winter and autumn seasons, with MIC values as low as 0.2 mg/ml in the DCM bulb extracts of T. violacea (winter) against K. pneumoniae and S. aureus. The amounts of total phenolic compounds in all plant samples were generally higher in spring compared to the other seasons. Condensed tannin, gallotannin and flavonoid levels, depending on the sample, were either higher in spring or winter except for H. hemerocallidea (corm) which had higher gallotannin levels in autumn. Total saponin levels were higher in winter in all plant samples. Although variation was observed in the phytochemical concentrations between the bulbs and leaves of each plant species, their antimicrobial activities were fairly comparable. Leaves may be used as substitutes for bulbs in the treatment of bacterial and fungal ailments.     

Seasonal variation in effect of spa therapy on chronic pain

This study sought to investigate whether the effects of spa therapy are subject to seasonal variation as suggested by conventional spa therapy research. A total of 268 female (age 31-90 yr) and 119 male (age 35-85 yr) patients with noninflammatory chronic pain were studied. Patients stayed at an Austrian spa for 3 wk and received 2-4 treatments per day, including mudpacks, massages, and exercise therapy. In different groups of patients for 2 yr, pain (self-assessed by questionnaire and Likert scales) and associated variables (mood, fatigue) were measured at the beginning, end, and 6 wk after spa therapy. Data were analyzed by multivariate analysis of covariance controlling for possible group differences between seasons and cosinor analysis. The effect of spa therapy on pain was seasonally dependent; short-term decrease of pain was best between April and June and medium-term decrease of pain was best between October and November, with a second minor peak in fall and spring, respectively. The magnitude of the seasonal variation was greater for back (∼30%) than for joint (∼20%) pain. Positive mood also improved most between April and June. The observed semi-annual variations of pain do not correspond to the well-known annual change in many physiological and psychological variables. The results suggest that the effects of spa therapy and possibly other related treatments, such as physical and alternative therapies, are subject to seasonal variation.     

Seasonal variation in effect of spa therapy on chronic pain

This study sought to investigate whether the effects of spa therapy are subject to seasonal variation as suggested by conventional spa therapy research. A total of 268 female (age 31–90 yr) and 119 male (age 35–85 yr) patients with noninflammatory chronic pain were studied. Patients stayed at an Austrian spa for 3 wk and received 2–4 treatments per day, including mudpacks, massages, and exercise therapy. In different groups of patients for 2 yr, pain (self-assessed by questionnaire and Likert scales) and associated variables (mood, fatigue) were measured at the beginning, end, and 6 wk after spa therapy. Data were analyzed by multivariate analysis of covariance controlling for possible group differences between seasons and cosinor analysis. The effect of spa therapy on pain was seasonally dependent; short-term decrease of pain was best between April and June and medium-term decrease of pain was best between October and November, with a second minor peak in fall and spring, respectively. The magnitude of the seasonal variation was greater for back (～30%) than for joint (～20%) pain. Positive mood also improved most between April and June. The observed semi-annual variations of pain do not correspond to the well-known annual change in many physiological and psychological variables. The results suggest that the effects of spa therapy and possibly other related treatments, such as physical and alternative therapies, are subject to seasonal variation.     

Seasonal variation of territory size with the Little Owl (Athene noctua)

Summary In a population of Little Owls (Athene noctua) at the Lower Rhine (FRG), the factors were studied that influence the size and shape of territories of this non-migrating, all-year territorial owl species. These studies were carried out between September 1984 and June 1987. The birds were individually marked with transmitter packages so that their locomotional movements could be monitored. Using a standard protable stimulus (a dummy with an attached loudspeaker) the territorial boundaries of 19 male Little Owls were surveilled during the different seasons of the year. Male Little Owls defended their territories in all seasons, but distinct seasonal changes of intraspecific aggressiveness and territory size were observed. The seasonal variations of territory size followed a common pattern in all studied Little Owls, in spite of individual differences in the size of the defended areas. The largest territories were defended in March/April during the courtship season . In May/June all male Little Owls reduced the size of their territories . This corresponds to the breeding and nestling period. The yearly minimum of territory size was reached in the summer months July and August when the fledglings were still fed in the parental territory. When the first-year birds started to disperse in autumn (September/October), the size of the defended areas of the adult tenants again increased . In winter (November to February), a further increase in territory size was observed for periods of warm weather . Male Little Owls, however, were less aggressive during winter than in the following courtship season. On cold winter days with a ground cover of snow territorial aggressiveness ceased. Pastures and meadows offered a continuous food supply almost throughout the year. In some seasons they were overproportionally represented in the territories of Little Owls compared to the general surroundings. In reaction to changing accessibility of food, the hunting ranges within the home ranges were shifted much faster than the boundaries of the defended territories. The significance of various factors contributing to the variability of territory size in Little Owls are discussed (e.g. availability of food, seasonal and individual differences in aggressiveness, experience in the occupied area, population density).     

Seasonal variation of thermoregulatory behaviour in the Hippopotamus (Hippopotamus amphibius)

The hippopotamus (Hippopotamus amphibius) spends more than 12 h a day in the water. Hippos are often submitted to water temperatures that vary with the seasons. We hypothesize that this difference between cool and warm water temperatures leads to variations in behavioural thermoregulation. We recorded the exposure of hippos to sunshine at the beginning and at the end of the dry season. Our results show that (1) sunshine exposure lasted much longer in cool water and (2) sun-bathing occurred during the hottest hours. It is therefore likely that in cool water hippos were cold and expressed an original behaviour of search for heat.