Seasonal Update (June 2023)

A burnt-tip orchid (_Neotinea ustulata_) is one of a number of orchids to flower during May and June. Many people are surprised to find orchids growing in their lawn, but some species are surprisingly common in lawns and roadside verges. - Credit: Marc Baldwin

Welcome to the start of meteorological summer. The sixth month of the Julian and Gregorian calendars, June hosts the summer solstice for the Northern Hemisphere and the winter solstice for the Southern Hemisphere. Junius is the Latin name for the month, although the etymology of the month remains a mystery. Competing theories for the origin of the name June include that it derives from iuniores, the Latin word meaning “younger ones”, which might correspond with May being named maiores (“elders”). It seems that June was also the month most favoured for Roman marriages, with some suggestion that the month was named after Juno, daughter of Saturn and the Roman goddess of love and marriage.

Weather update

May started on a broadly summery note, with temperatures across much of the UK into the mid- to high teens Celsius thanks to high pressure over Scandinavia. Towards the end of the first week a low-pressure system pushed in from the Atlantic bringing more cloud and showers and dropping temperatures, most notably in Republic of Ireland and Wales with temperatures holding up for longest in the east of England. Most of Europe and the whole of the UK remained bathed in mild air for the Coronation weekend, while Scandinavia and parts of northern Russia saw much colder conditions.

GEFS 2m temperature chart for May Day showing the relatively chilly start to the month across much of Europe. - Credit: WX Charts

The second week was unsettled and windy at times, but temperatures held up in the mid-teens by day and in the sunshine it felt very spring-like. Indeed, after a cloudy and misty start to both days of the middle weekend, the sun broke through and it was bordering on summery, with temperatures widely into the high teens and low 20s Celsius (mid- to high 60s Fahrenheit). Despite being a rather dull spring, the second half of May was largely warm and sunny, albeit continuing windy, across much of the UK, only the odd weakening band of rain moving across Ireland, Scotland and northern England. Porthmadog in Wales saw the warmest UK day of 2023 so far, nudging just over 23C (73F) on 21st.

Outside of the UK, torrential rainfall in central and eastern Africa resulted in devastating floods in Rwanda and Somalia, with at least 130 people killed and villages virtually washed away. Similarly, two storms brought heavy rain and flooding to Italy. South-east Asia and Central America were under harsh heat last month, with Honduras and Nicaragua both exceeding 40C (104F), the former exceeding the national record for May. Costa Rica and Panama were in the high 30s Celsius. Vietnam and Laos both set new national heat records on 6th May at 44.1C (111.4F) and 43.5C (110.3F), respectively. The second weekend saw temperatures rise above 25C in the Baltic countries and to 32C in Greece. The following week was very hot in the eastern Mediterranean (above 35C/95F in Turkey and Cyprus), while it was much cooler than average in the Central Mediterranean.

Tropical areas were at record heat levels nearly all over. Indonesia and Malaysia saw new monthly highs, topping 36C (97F), while north Africa was subjected to a punishing heatwave during the second half of May.

Website news

A new section covering the gestation and litter size of the Chinese water deer also went live last month.

News & discoveries

Buzz off? Bees are known to be particularly sensitive to electromagnetic fields, which they use to help navigate their surroundings and even to establish whether a flower has recently been visited by another bee. New research on honeybees by scientists at the University of Talca in Chile suggests, however, that the strong electromagnetic fields generated by transmission towers carrying high voltage power lines can affect their ability to store memories, navigate and, overall, their foraging efficiency.

Water, water, everywhere? We're all aware that freshwater is essential for most life on earth, and much of the freshwater on Earth is tied up in glaciers. The bulk of freshwater resides in lakes and reservoirs, however, together accounting for around 87% of the Earth's global freshwater supply. A recent satellite assessment of nearly 2,000 of the world's largest lakes and reservoirs suggests that just over half are losing water; storing less water than they did three decades ago. Overall, the loss is in the order of 544 million litres (144 million gallons) of water. The researchers point to a warming climate and unsustainable human population as the main culprits.

Colliford Lake, a reservoir in eastern Cornwall, is below normal levels this summer following a dry spring off the back of a dry winter and hot summer. Many of the world's reservoirs are holding less water than they historically have. - Credit: Phil Baldwin

Oh, I do like to be beside the seaside. Most of us enjoy a trip to the beach, and it was common as far back as the 17th century for physicians to prescribe a swim in the sea as a tonic for all manner of ills. More recently, a survey of 15,000 people from Australia and 14 European countries has shown that people living near and/or visiting the seaside is consistently associated with better health, irrespective of the country you're from or how wealthy you are.

Fearless flu. H5N1, a particularly potent strain of avian influenza, or bird flu, has been in the news a lot recently after several outbreaks that resulted in restrictions being imposed on fowl keeping in Britain, but it's not only our feathered friends that are susceptible. New data on infection of 67 wild mammals in the US, including foxes, raccoons, skunks and bobcats, has revealed almost 80% showed symptoms of neurological disorders. Seizures, problems with balance and coordination, tremors and a lack of fear of people were reported in the infected individuals, suggesting that bird flu may cause abnormal behaviour among some mammal species. There remains no evidence, however, that the virus can be passed to humans from wild mammals.

Seasonal highlight – Kids, fawns and calves: the season of baby deer

There are six species of deer found wild in the UK—red, roe, fallow, Japanese sika, Chinese water deer, and Reeves's (or Chinese) muntjac—and all will have young at this time of year, although muntjac aren't seasonal breeders and can have young at any time. Juvenile deer, those less than one year old, have different names depending on the species to which they belong. Red and sika deer have calves, fallow, muntjac and Chinese water deer have fawns, and roe deer have kids (occasionally also called fawns).

This month's feature will briefly cover the biology and behaviour of these newborn deer. It is important to say, from the outset, that if you find a baby deer lying up alone, with its mother nowhere in sight, please do not touch it. As we shall see, this is perfectly normal behaviour.

A Red deer (Cervus elaphus) hind licking her newborn calf. - Credit: Dave Webb

Red (Cervus elaphus) calves: Red deer rut during the autumn (September and October) and in some populations three-quarters of the hinds (females) will conceive in the last three weeks of October. Following a gestation of about eight months, the hind will leave the herd and move to an area with good cover to give birth. In most cases the hind will deliver only a single calf; twins are known in high quality habitats, but typically account for less than 1% of births. The size of the calf varies according to the condition of the mother, but most newborns weigh in at around 6.5kgs (just over 14 lbs). The mother will lick the calf clean and it'll suckle shortly afterwards; it'll be able to stand fully after about 40 minutes. The hind will leave the calf lying up in the vegetation and move away to feed or rest nearby, returning to suckle periodically; the calf will be suckled between five and ten times per day, although this may be condensed into only three or four visits.

Once the calf is about a week old it'll start to choose its own hiding spots. If disturbed or alarmed, the calf will let out a high-pitched scream/cry, which will bring the mother (sometimes several hinds) rushing back. While lying up in cover calves are vulnerable to predators, including foxes and domestic dogs, less so by the time they start following their mothers at around 10 days old. When the calf is mobile the hind will rejoin the herd and the calves often form crèches, resting and playing together. Weaning is completed at around eight months old, but they may continue to suckle until they're ten months of age - the hind seems to grow increasingly impatient as the suckling period wears on, and will sometimes walk away mid-suckle.

Sika (Cervus nippon) calves: We know considerably less about the breeding biology of sika than we do their cousins, the red deer. Like red, they rut during the autumn (although peaking in late October or early November) and 80-90% of hinds in good habitat will conceive in a given year. Gestation is just over seven months (average pregnancy is 220 days), with most calves born between early May and late June. Sika deer are, however, less well synchronised in their breeding cycle than our other deer species, resulting in some calves being born as late as August or September - there are even records of births in November. Typically, only a single calf is born to a hind, although there are very occasional records of twins. The only record I'm aware of here in the New Forest was a pair of male calves born to a captive hind at Denny Lodge in 1971.

The only relatively comprehensive description of sika birth I'm familiar with was given by Mohamed Fouda and his colleagues at Mansoura University in Egypt in the late 1980s. Fouda and his co-workers observed 17 hinds at two British zoos, noting their birthing behaviour was very similar to that of the red deer, although they did not segregate themselves from the rest of the herd before birth. Calves were quickly licked clean by the mother and could stand fully after about 30 minutes. The average first suckling happened about 40 minutes after birth and the calf remained with its mother for about 4.5 hours before finding a hiding place.

A Manchurian sika calf lying low waiting for its dam to return. - Credit: Marc Baldwin

For the first few days after birth the calf is suckled frequently (4-5 times per day), with the suckling frequency declining to once or twice per day by the time the calf is two weeks old. Sika calves grow rapidly from an average birth weight of about 5kg (just under 11 lbs) to ten times that by about ten months old. The calf is weaned at around eight months old and sexually mature at about 16 months.

Fallow (Dama dama) fawns: Fallow deer rut during the autumn (peak around mid-October) and studies in both Richmond Park and the New Forest have shown that 80-100% of does (females) conceive each year, depending on age and habitat quality. Development of the foetus is initially quite slow, increasing when a placental connection is formed. Gestation takes about 7.5 months, and results in a fawn weighing about 4.5kg (8 lbs) during late May or June. Typically, only a single fawn is produced per doe, although there is at least one record of twins born to a 12-year-old captive doe; several reports exist of a doe with two fawns, but it is generally considered that this is another doe's fawn who has just tagged along and isn't evidence of twin birth. As with sika, fallow does do not appear to leave the herd to give birth, although the group may spend more time feeding in areas with plenty of ground cover and the new mother often acts aggressively to any deer that stray too close. Observations from captivity describe does pacing their enclosures uncomfortably giving high-pitched bleats every second-or-so, suggesting that labour is painful. Labour to birth takes an hour or two and captive observations suggest that the fawn may be delivered as quickly as 15 minutes after the doe's waters break.

A fallow doe suckling her newborn fawn. Like most newborn mammals, fawns cannot evacuate their own bowls and need to be stimulated by their mother licking their rear end, typically while suckling. - Credit: Marc Baldwin

The fawn is licked clean by the doe, who also eats the afterbirth (a tactic that not only replenishes lost protein, vitamins and minerals, but also reduces attractants for predators). The fawn can stand within minutes, although it is very unsteady on its feet, and will suckle within the first hour. The doe will rest with, or near, the fawn for the first couple of hours after birth, before she moves away to feed, leaving the fawn secreted in the undergrowth. Disturbed fawns make a piercing cry that will bring the doe, and often her fawn from last year, running to investigate; unlike Red deer, however, most of the herd will ignore the cry. As the fawn grows it will spend more time following its mother and, by mid-July, they can be seen playing in small groups; larger crèches form by mid-August and the does may also congregate in larger groups to feed.

Roe (Capreolus capreolus) kids: Roe deer rut during the summer (late July/early August) and undergo embryonic diapause, also known as delayed implantation, through late summer and autumn, during which the blastocyst is kept in 'suspended animation'. Development reactivates in late December or early January. In most species practising diapause the female releases a burst of progesterone as a 'wake-up call' to the embryo, causing development to resume. In roe deer, however, the embryo has an internal clock and, at a pre-set time, it sends out its own hormonal signal to the mother, who responds by releasing oestrogens that trigger the embryo's rapid growth and placental attachment. The size and condition of the female seems to determine when/if she ovulates and how many corpora lutea are produced (rather than it being age dependent), while the number of foetuses is strongly influenced by the weather during the winter - heavy rain and prolonged frost/snow are generally detrimental to foetal survival. In very productive habitats, 70% of the does will fall pregnant.

A newborn Roe deer (Capreolus capreolus) kid lying up in a hay field. It's normal for deer mothers to leave their young lying up in a secluded spot. If you find one, please leave it where it is. Do not touch it unless it's in imminent danger. - Credit: Sharon Scott

The doe will gestate for about nine months, which includes a diapause of around three months, and give birth in late May or early June. Despite being relatively uncommon in other deer species, twins are frequently observed, accounting for an estimated 75% of births. Roe give birth to a single offspring (kid) in about 20% of cases and very occasionally triplets (about 5% of births) or quadruplets (less than 2% of births). Does seem to prefer giving birth to their kids in areas with long grass to act as cover; one study, published in 1975, reported that 74% of does in their study gave birth in meadows, with grass of 20-50 cm (8-20 inches) apparently preferred. The doe will typically stand to give birth and several authors have noted that the labour and birth appear painful. When the kid is born the mother attends to it immediately, licking it clean, although this does depend somewhat on the experience of the mother - inexperienced does sometimes wander off and leave the kid for a while before returning to tend to it. When twins have been conceived, they can be born several hours apart. At birth, kids weigh about 1.2kg (1 lb 3 oz).

While the kid is still wet, if finds it difficult to stand and the doe may lie down to suckle it, after which it sleeps. The doe doesn't lie with her kid(s), but instead moves around the area feeding as resting as normal, although she is often not far from their hiding place. If twins are born, they rarely lie up together for the first week or so, which presumably reduces the possible scent trail and makes them a little less vulnerable to predators.

Chinese Water (Hydropotes inermis) fawns: Chinese Water deer rut during the winter (peak in December), although the initial courtship may begin as early as October. This species evolved in a very unstable, but productive, habitat and consequently are among the most fecund deer known today. A doe will typically produce two or three fawns (four or five are known) after a gestation lasting between about five and seven months. In the UK, most fawns are born in late May and early June, although some earlier and later records exist, and does don't seem to choose any particular habitat in which to give birth, with fawns found in open fields, fens and woodlands. The mother licks the fawns clean immediately after birth and will consume the afterbirth shortly afterwards. At birth a fawn will typically weigh between 600g (1 lb 5 oz) and a kilo (2 lb 3 oz); it can stand fully and suckle within an hour. Chinese Water deer fawns are much more mobile than the newborns of other species, moving up to 100 m (330 ft) during their first day of life.

A Chinese water deer doe with her recently born fawn. The mother will return to the fawn periodically through the day and night to suckle and clean it, after which there may be a short bout of play. - Credit: Marc Baldwin

The fawns will spend their first couple of weeks lying up in vegetation (generally on their own, although they do sometimes lie-up with siblings) waiting to be fed; the doe returns several times each day to suckle and groom them. Once fed and groomed, the fawns move away to find another hiding spot. The fawns are weaned by about three months, although they start taking small quantities of vegetation from two or three days old.

Reeves's muntjac (Muntiacus reevesi) fawns: Unlike our other deer species, muntjac do not have a seasonal breeding cycle; the buck will remain fertile throughout the year, even while antlers are regrowing. Muntjac don't have the complex rutting rituals observed in some of our larger species - the male is attracted to the female's scent and he follows her for a short period before they mate. The doe gestates for about seven months before giving birth to a kitten-sized fawn weighing around 900g (about 2 lbs). Typically, only a single fawn is produced, although twins are reported occasionally. Fawns will stand and suckle within an hour and, much like those of the Chinese water deer, are highly mobile; one fawn was observed to change hiding spot three times in the first six hours of life. The fawn will supplement milk with vegetation at two or three days old and is fully weaned by about 8-12 weeks. Observations in captivity suggest that the fawn can survive on its own from around 14 days old. The doe will come back into season about 36 hours after the birth of her fawn and so many wild does are in a nigh-permanent state of pregnancy.

A Reeves' muntjac doe suckling her fawn. - Credit: Peter Trimming

For a round-up of Britain's seasonal wildlife highlights for early summer, check out my Wildlife Watching - June blog.

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